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US Senate rejects amendment to block Trump from unilaterally declaring war on Iran

Measure sought to bar US president from going to war with Iran without oversight from Congress
Trump has imposed series of sanctions on Iran amid escalating tensions (Reuters/File photo)

The US Senate has voted down an amendment that sought to bar President Donald Trump from being able to declare war on Iran without authorisation from Congress.

The measure - an amendment to an annual defence policy bill that would "prohibit unauthorised military operations in or against Iran" - was defeated in a 50-40 vote on Friday afternoon, Reuters reported.

The bill, the National Defense Authorization Act (NDAA), passed in the Senate on Thursday.

But lawmakers made the unusual decision to hold the amendment vote on Friday after some Democrats and Republicans called for a debate on the matter, the news agency said.

The vote comes amid ongoing tensions between Washington and Tehran - and as US lawmakers from both major parties continue to voice their opposition to the Trump administration's policies towards Iran.

A timeline of US-Iran tensions

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Tensions have skyrocketed between the Washington and Tehran since US President Donald Trump announced last May that he was pulling out of the 2015 Iranian nuclear deal.

Here's a timeline of key events that have led to, and marked, the recent escalation:

8 May 2018: US President Donald Trump announces plans to pull out of a 2015 nuclear deal with Iran. Under that agreement, the Iranian government agreed to curb its nuclear programme in exchange for a lifting of international sanctions.

Trump also says Washington will reimpose "the highest levels of economic sanctions" on Tehran.

5 November 2018: The US reimposes sanctions on Iran's oil, banking and transport sectors. At the same time, Trump says he wants to gradually impose sanctions on the Iranian oil industry, citing concerns about upsetting energy markets and causing global price spikes.

8 April: The Trump administration blacklists Iran's elite military force, the Islamic Revolutionary Guard Corps (IRGC). The move marks the first time Washington has formally labelled another country's military a terrorist group.

30 April: Iranian President Hassan Rouhani signs a bill into law that declares all US troops in the Middle East as terrorists, and defines the US as a state-sponsor of terrorism.

2 May: The US stops issuing waivers to countries that import oil from Iran. Those waivers had allowed certain states, including Turkey, China, Japan, India and South Korea, to keep buying Iranian oil, despite American sanctions - and provided a lifeline for Tehran.

6 May: US National Security Adviser John Bolton announces that the Trump administration is deploying an aircraft carrier, as well as ships and bombers, to the Gulf. The move was meant to send a "clear and unmistakable message" to the Iranian government, Bolton said, amid intelligence reports that Tehran was planning attacks against American troops in the region.

7 May: Iran says it plans to withdraw from parts of the 2015 nuclear agreement with major world powers. The move comes one year after US President Donald Trump withdrew from the deal.

8 May: The Trump administration announces a new round of economic sanctions that will target Iran's metals trade - iron, steel, aluminium and copper, specifically.

9 May: As the drums of war began to beat louder in certain circles in Washington, Trump tells reporters that he "would like to see them [Iran] call me" - a sign the US president is perhaps seeking to de-escalate the situation.

12 May: The United Arab Emirates says four oil tankers were damaged in "acts of sabotage" off the coast of Fujairah, just outside the Strait of Hormuz. The UAE did not assign blame for the incident, but said it would launch an investigation into what happened.

13 May: Mike Pompeo makes a surprise visit to Brussels, where he seeks to get European leaders on board with Washington's "maximum pressure" strategy against Tehran. The US secretary of state gets a lukewarm reception, however, with the European Union's foreign policy chief instead urging the US to show "maximum restraint".

14 May: Iran's Supreme Leader Ali Khamenei says the country will not go to war with the US. "Neither we nor they - who know war will not be in their interest - are after war," Khamenei says.

15 May: Anwar Gargash, the UAE's minister of state for foreign affairs, says the country is committed to "de-escalation" with Iran, while refusing to assign blame for the 12 May "sabotage" of the oil tankers.

That same day, the US orders non-emergency government employees to leave Iraq, citing fears of an imminent attack by Iranian-backed proxies in that country.

19 May: A Katyusha rocket is fired into Baghdad's Green Zone, an area that houses government offices and foreign diplomatic missions, including the US embassy in Iraq.

21 May: A previously unknown Iraqi group claims responsibility for the rocket fired into the Green Zone. The Operations of Martyr Ali Mansour says the attack is retaliation for Trump's decision to pardon a soldier who killed an Iraqi detainee in 2009.

In Washington that same day, US lawmakers are briefed by members of the Trump administration about its claims that Iran poses a threat to the country. Several members of Congress tell reporters they left the meetings unconvinced.

24 May: Washington announces plans to deploy 1,500 additional troops to the Middle East to counter Iranian threats, a decision Iran blasted as "extremely dangerous".

28 May: US National Security Adviser John Bolton says the attack on four vessels off the Emirati coast was caused by "naval mines almost certainly from Iran".

30 May-1 June: Saudi Arabia hosts a summit in Mecca to discuss recent tensions with Iran. On the eve of the talks, Riyadh blasts what it called Iranian "interference" in the region and demanded "firmness" over attacks in the Gulf.

7 June: The US imposes sanctions on Iran's largest petrochemicals holding group, accusing Persian Gulf Petrochemical Industries Company of providing financial support to an engineering firm with ties to the IRGC.

13 June: Two oil tankers suffer damage after an unspecified attack in the Gulf of Oman. Hours after the incident, US Secretary of State Mike Pompeo points the finger at Iran, without providing evidence to back up his claim.

Iran immediately denies it was involved in the attacks, accusing Washington of seeking to derail diplomatic efforts to de-escalate the situation.

14 June: The head of the United Nations calls for an independent investigation into the incidents in the Gulf of Oman.

Earlier in the day, US Central Command releases a video that it says shows Iranian IRGC members removing an unexploded mine from one of the damaged ships. That comes after Trump himself says the incident has Iran "written all over it".

Meanwhile, the owner of the Japanese vessel says crew members reported seeing objects flying towards them - which would appear to refute the US's version of events. "The crew told us something came flying at the ship and they found a hole," the owner says. "Then some crew witnessed the second shot."

17 June: The US will send roughly 1,000 additional troops to the Middle East, Defense Secretary Patrick Shanahan announces.

20 June: Iran says it shot down a US military drone entering Iranian airspace near the Straits of Hormuz. A US official confirms that a drone was shot down but says it was in international airspace.

21 June: US President Donald Trump says he ordered and then aborted a military strike on Iran roughly 10 minutes before the operation took place.

Fighter jets were in the air to strike multiple Iranian military installations in response to Iran's shooting down of an unmanned US drone a day earlier, according to US media reports.

Trump says he called off the strike after US generals reportedly told him the attack would kill 150 Iranians. The US operation was "not proportionate", the US president says.

24 June: The US imposes a new round of sanctions on Iran, this time targeting the country's supreme leader, Ayatollah Ali Khamenei.

25 June: Trump threatens Iran with "obliteration" if the country were to strike American targets. His comments come after Iranian President Hassan Rouhani called the White House "mentally retarded" and vowed that Tehran would not back down from US sanctions. 

Also on Tuesday, Iran's Foreign Minister Mohammed Javad Zarif tweets an article written by John Bolton in 2017, which outlines how the US should back out of the nuclear deal and detailing why the Iranians would not want to negotiate once the US withdraws.

28 June: The US Senate votes down an amendment that sought to bar Trump from being able to declare war on Iran without authorisation from Congress.

4 July: A supertanker suspected of carrying Iranian crude oil to Syria in violation of EU sanctions is detained in Gibraltar. Senior Iranian officials deny claims the tanker was headed to Syria. 

5 July: A senior Islamic Revolutionary Guard Corps (IRGC) commander suggests that Iran should seize a British oil tanker if the Iranian vessel detained off Gibraltar is not released immediately.

9 July: General Joseph Dunford, a top US general, announces plans to set up a coalition of allied countries willing to patrol key waterways in the Gulf region. 

Dunford says the US military would provide command ships and surveillance technology, while its allies would escort ships and patrol the Strait of Hormuz and Bab el-Mandeb.

11 July: British officials say three Iranian boats attempted to "impede the passage" of a British oil tanker in Gulf waters, forcing a UK warship to intervene. Iran denies the accusation

Meanwhile, Gibraltar police announce the arrest of the captain and chief officer of the Iranian supertanker on suspicion that the ship had breached EU sanctions on Syria on 4 July. 

Police also seize documents and electronic devices from the ship, which remains in custody. 

12 July: US lawmakers approve a measure that would force President Donald Trump to seek congressional approval before ordering military strikes against Iran.

16 July: Iran says it has ruled out entering into negotiations over its ballistic missile programme, directly contradicting statements made by US Secretary of State Mike Pompeo earlier that same day.

18 July: Trump says American warship USS Boxer downed an Iranian drone in the Strait of Hormuz. But top Iranian officials deny the report.

31 July: Washington imposes sanctions on Iran's Foreign Minister Zarid.

Last month, the US accused Iran of seeking to attack American forces and their allies in the Middle East. It also blamed the Iranian government for a string of attacks in the Gulf - allegations that Iran has repeatedly denied.

While some senior US officials, including Trump's national security adviser John Bolton, have been accused of beating the drums of war, US lawmakers from both major parties have sought to rein in the White House.

'Congress should have the guts and the backbone to go on the record on any war before we order our troops into harm's way'

- Senator Tim Kaine

"A war with Iran would be a colossal mistake," Democratic Senator Tim Kaine, one of the amendment's co-authors, said on Twitter before Friday's vote.

"Congress should have the guts and the backbone to go on the record on any war before we order our troops into harm's way," Kaine wrote.

But Mitch McConnell, a Republican senator and Trump ally, lambasted his colleagues for even proposing such a restriction on the White House.

The amendment "would hamstring the executive branch from reacting quickly - and in modern warfare, time is of the essence", he said on the Senate floor.

"This amendment could even restrict our military from acting to prevent an imminent attack."

The AUMF

But several US lawmakers have argued that Trump cannot rely on a 2001 law, the Authorization for Use of Military Force (AUMF), to greenlight a war against Iran without an OK from Congress.

The AUMF was passed after the 9/11 attacks, granting the US president the authority to use military force against the Taliban and al-Qaeda in Afghanistan without congressional approval.

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The legislation has been expanded in scope several times since 2001, and a second AUMF passed in 2002 was used to justify the US invasion of Iraq a year later.

Former US President Barack Obama also invoked the AUMF to carry out drone strikes against militant groups in Yemen, Syria, Somalia and elsewhere.

Barbara Lee, a Democrat in the House of Representatives, has been at the forefront of efforts to stop Trump from using the AUMF to declare war on Iran.

On Friday, she criticised Trump for pulling out of the 2015 nuclear deal under which Tehran agreed to curb its nuclear programme in exchange for a lifting of international sanctions.

"Trump unilaterally violating the Iran deal has alienated us from our allies & brought us closer to a military confrontation with Iran. It's time to stop this reckless warmongering and return to the negotiating table. #NoWarIran," Lee wrote on Twitter.