The coalition estimates that there are between 3,000 and 4,000 militants in Raqqa
The global coalition fighting the Islamic State will soon begin a final assault on Raqqa, France said on Friday.
"Today, we can say that Raqqa is surrounded and the battle will begin in the coming days," French Defence Minister Jean-Yves Le Drian told France's CNEWS television.
"This will be a very hard battle but essential."
The coalition estimates that there are between 3,000 and 4,000 militants in Raqqa, a city of about 300,000, and the Islamic State group’s de facto Syrian capital.
On the ground in Syria Friday, the US-backed Kurdish-Arab alliance, the Syrian Democratic Forces, reached the entrance to the Tabqa dam where they are clashing with IS, Jihan Sheikh Ahmed, the SDF's spokeswoman for the campaign said.
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The US-led coalition against IS air-dropped SDF fighters near Tabqa late on Tuesday on the southern side of the Euphrates, and other SDF militia fighters were already present on the river's northern bank.
The dam, the biggest on the Euphrates, stretches 4km across the river to the southern bank and provides one of the few land crossings remaining after the destruction of many bridges during the conflict.
Tabqa is about 40 km (25 miles) west of Raqqa, which Islamic State has used for years as one of its main bases of operations, including to plan and direct attacks overseas, and which sits along the northern bank of the Euphrates.
The US military has provided air and artillery support involving Apache helicopter gunships to help the SDF in the battle for the dam and the surrounding area, as well as airlifting in fighters.
The militant group is also under pressure in its sister city of Mosul in Iraq, where Iraqi forces are closing in on IS.
A European diplomat, who did not want to be named, said the situation surrounding the Raqqa offensive remained "complex".
"The Americans are still in the review process. Trump did not make a decision (on who will take Raqqa), but it is clear that on the ground it is the SDF option that is developing."
"The operation to besiege Raqqa will take several weeks and that will then lead to the official launch of the operation," another SDF spokesperson, Talal Sello, told AFP.
"The first goal of the SDF is to control Tabqa city (next to the dam) or besiege it completely before starting the battle for Raqqa," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights monitor.