The Syrian Democratic Forces (SDF), a US-backed group, says it will soon begin a final attack to capture Raqqa, ISIL's self-proclaimed capital in northern Syria, just days after seizing a key town to the west and an adjacent dam.

The announcement on Friday followed US President Donald Trump's decision on Monday to approve direct arms shipments to the SDF's Kurdish elements - the Kurdish People's Protection Units (YPG) - to "ensure a clear victory" over ISIL.

SDF commander Abdul Qader Hevdeli said on Friday the push to Raqqa "will be in the coming period of time.

"I can't specify exactly; I believe entering and storming the city will happen at the start of the summer," he said in a news conference in Tabqa city, which the SDF took from ISIL on Wednesday.

Hevdeli said the US arms shipments would "arrive soon" and added that Raqqa would be captured without help from other forces.

"We don't need any other forces to be our partner," he said. "We thank anyone who wants to help but our forces are capable enough to liberate Raqqa and go further. For those who want to help ... they must first solve their problems in their own countries."

The SDF's war on Raqqa has already seen the mainly Kurdish group capture large swaths of the surrounding province with help from the US-led coalition bombing ISIL in Iraq and Syria.

This week, following months of fighting, the SDF seized the strategic town of Tabqa, to the west of Raqqa, and a major hydroelectric dam nearby.

"This victory in Tabqa over ISIL has been a big prize for the SDF," said Al Jazeera's Charles Stratford, reporting from Gaziantep on the Turkish side of the Syria-Turkey border.

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Tabqa lies on the banks of the Euphrates River, about 55km west of Raqqa. It was taken by ISIL in August 2014, following its capture of Raqqa, a city with at least 300,000 residents, in early 2014.

The battle for Tabqa was marked by fears that the dam would be severely damaged and collapse, leading to massive flooding downstream.

The SDF said in a statement that Tabqa would be turned over to a civilian council once fully secured. It also said the authority that oversees the Tabqa dam would remain "a national Syrian institution that will serve all the regions of Syria without exception".

Washington's decision to arm the YPG, the SDF's main faction battling ISIL, reignited a dispute with Turkey, with President Recep Tayyip Erdogan calling for an "immediate" reversal.

Turkey views the Kurdish Peoples' Protection Units as the Syrian extension of the outlawed Kurdistan Workers' Party, which has fought the state in the southeast of Turkey since 1984 and is considered a "terrorist group" by the US and the EU.