Ankara: US Defence Secretary Jim Mattis told his Turkish counterpart that weapons provided to the Kurdish YPG militia in Syria would be taken back once Daesh was defeated, Turkish defence ministry sources said on Thursday.

In a letter to Turkey’s Defence Minister Fikri Isik, Mattis said the United States had informed Turkey about the weapons it had given the YPG and that it would provide monthly lists of the arms supplied, the sources said in a statement.

Relations between the two Nato allies have become strained due to the support the United States has given the YPG, which Turkey has fought in northern Syria, to support the campaign against Daesh.

In his letter, Mattis told Isik that the United States would take determined measures to address Turkey’s security concerns, the sources said, and that Arabs would comprise 80 per cent of the forces to capture Syria’s Raqqa from Daesh.

The YPG is a leading part of the US-backed Syrian Democratic Forces (SDF) which launched an operation earlier this month to capture Raqqa, Daesh’s de facto Syrian capital.

Turkey has said that it would retaliate against the YPG if it felt a threat from the group.

SDF militias are closing in on Daesh’s Syrian stronghold of Raqqa, taking territory on the south bank of the Euphrates River with the aim of encircling the city.

The Syrian Democratic Forces began an offensive two weeks ago to seize the northern city from Daesh, which overran it in 2014.

Nouri Mahmoud, spokesman for the Kurdish YPG militia which is part of the SDF, told Reuters Daesh had been ousted from the suburb of Kasrat al Farj as the SDF moved in along the southern riverbank from the west.

When the campaign began the SDF had Raqqa, which sits on the Euphrates’ northern bank, surrounded from the north, west and east. Although Daesh controlled the south bank of the river, coalition air strikes had destroyed the bridges connecting it to the city.

The SDF is now trying to enact a siege of the city by taking the southern bank. The forces are a couple of kilometres from achieving this aim.

The Syrian Observatory for Human Rights war monitor said on Wednesday SDF forces had moved along the southern river bank to reach the eastern edge of Kasrat Al Farj, in the area between the new and old bridges into Raqqa.

Daesh is also facing defeat in its Iraqi stronghold of Mosul and is being forced into retreat across much of Syria, where Deir Al Zor in eastern Syria is its last major foothold.