US may send as many as 250 more troops to Syria

US President Barack Obama will on Monday announce plans to send as many as 250 more military personnel to Syria, according to a senior administration official, intensifying US assistance to rebels as a ceasefire falters.

Obama "tomorrow will announce that he has authorised up to 250 additional forces deploying to Syria," the source said, adding that the president would confirm the deployment in a speech in the northern city of Hanover.

The deployment will come on top of 50 special operations forces Obama deployed to Syria last year, two US officials told Reuters. One official said the announcement would come in a speech Obama plans to give in Hanover, Germany, on Monday.

US troops in Syria are mandated to advise and assist Syrian rebel and anti-Islamic State forces.

Obama is currently in Germany for talks with Chancellor Angela Merkel.

The pair will be joined Monday by leaders from Britain, France and Italy, a meeting called at Obama's request and which looks set to focus on the fight against the Islamic State (IS) group.

"The president has authorised a series of steps to increase support for our partners in the region, including Iraqi security forces as well as local Syrian forces” who are taking the fight to IS, said the official.

Obama is set to announce the decision at the Hanover trade fair before the meeting with European leaders.

On Sunday, Obama pressed for parties to the Syrian conflict to return the negotiating table and "reinstate" a faltering internationally-brokered ceasefire.

That was the clearest indication yet that the White House believes the increasingly troubled ceasefire has disintegrated as government and rebel bombardments claimed 26 lives Sunday.

The White House has argued that the ceasefire, while imperfect, is worth pursuing and is the only way out of the brutal five-year war. 

But its stance is bringing Washington and its allies into ever more conflict with rebel groups on the ground, which continue to be on the receiving end of government attacks.

Pressure on Obama is increasing in the US, which in is the throes of a fiercely fought presidential election race, and from European allies who want to halt a massive influx of refugees.

Many of Obama's critics have called for a safe zone to be established, something that could bring Western militaries into direct conflict with Russian and Syrian forces already in the area.

Obama insisted that establishing a safe zone "is not a matter of an ideological objection on my part".

"As a practical matter, sadly, it is very difficult to see how it would operate short of us essentially being willing to militarily take over a big chunk of that country."

Obama has come under criticism for his handling of Syria's war, with opponents saying he could have done more to stem the bloodshed.

But the US president - who came to power vowing to withdraw US troops from Iraq and Afghanistan - has stood fast in his opposition to plunging the US into another ground war in the Muslim world.