Two US senators visited the northern Syrian town of Manbij on Monday, where talks between Washington and Ankara narrowly avoided a stand-off between the NATO allies earlier this year.

Lindsey Graham from South Carolina and Jeanne Shaheen from New Hampshire toured the town with members of the Manbij Military Council.

"The aim of the visit was to see the security situation in Manbij," said its spokesman Sherfan Darwish.

The MMC is linked to the Syrian Democratic Forces, an alliance of Kurdish and Arab fighters that ousted the Islamic State group from Manbij in 2016 with help from a US-led coalition.

American and French coalition troops are still stationed in Manbij, but there were fears earlier this year they could be caught up in a clash with Turkey.

Ankara had pledged to march on Manbij after seizing the nearby area of Afrin from Kurdish fighters it sees as "terrorists".

But the US and Turkey agreed on a "roadmap" last month that avoided a confrontation, and Turkish troops began patrolling areas to the town's north under the deal.

In footage published by a local SDF-linked outlet on Monday, Graham could be seen telling MMC commanders the US would not withdraw from the area.

"I will tell President (Donald) Trump it's important that we stay here to help you. You're friends of the United States and if we leave, it will be terrible," Graham said.

Trump has said he intends to pull US troops out of Syria but his defence establishment has stressed it wants to retain a presence to fully defeat IS.