US, Turkey 'will work together' in Syria: Tillerson

US Secretary of State Rex Tillerson on Friday said NATO allies Turkey and the United States would work together in Syria after a spike in tensions over the conflict.

"We are not going to act alone any longer, not US doing one thing, Turkey doing another," Tillerson said in Ankara after talks with Turkish counterpart Mevlut Cavusoglu.

"We will work together... we have good mechanisms on how we can achieve this, there is a lot of work to be done," he said.

A prime task of Tillerson on his trip to Ankara is to allay Turkish anger over US policy in Syria, a dispute which has ignited the biggest crisis in bilateral ties since the 2003 Iraq war.

Washington has warned that Turkey's operation against the People's Protection Units (YPG) Kurdish militia in the Afrin region of Syria risks distracting from the fight against jihadists.

He added that Turkey and the United States had to solve the tensions surrounding the Kurdish militia-held Syrian town of Manbij - which Ankara has threatened to attack - as a "priority".

The United States has up to 2,000 troops stationed in Manbij, raising fears of a confrontation between the two NATO allies.

"Manbij is going to be given priority in our joint working effort," he said.

The town was once held by Islamic State (IS) militants before they were pushed out by Kurdish militia and Tillerson said it was vital it did not fall again into jihadist hands.

Tillerson said Manbij will be a "topic of discussion" with Turkey to ensure the city remains in control of allied forces of the United States.