MOSCOW -- Top Russian and Turkish ministers agreed during a meeting in Moscow on Saturday to maintain co-operation in northern Syria as U.S. forces prepare to withdraw and Turkey threatens to launch a military operation against U.S.-backed Kurdish forces controlling nearly a third of the country.

Russian Defence Minister Sergei Shoigu said before the talks began that they would focus on the situation in and around Idlib, as well as "what can and should be done" when the U.S. withdraws from Syria.

After the meeting, Russian Foreign Minister Sergei Lavrov told reporters that much of the discussion focused on the pending U.S. withdrawal, and that Russia and Turkey managed to agree on co-ordinating their steps in Syria "to ultimately eradicate the terrorist threat."

Turkey's official Anadolu news agency said the meeting lasted an hour and a half. Turkish Foreign Minister Mevlut Cavusoglu said Russia and Turkey have a "shared will on cleaning Syria from all terror organizations," and added Turkey would continue its "close co-operation" with Russia and Iran in Syria and the region.

The Syrian military said it entered the Kurdish stronghold of Manbij on Friday as part of an apparent agreement between the two sides. The Kurds are looking for new allies to protect against a threatened Turkish offensive as U.S. forces prepare to leave.

With President Donald Trump's surprise decision to withdraw troops earlier this month, Turkey announced it will hold off on a threatened offensive against Kurdish militants that it considers terrorists. It has, however, continued amassing troops at the border as it monitors the situation.

The movements follow days of equipment transfers across the border into a Turkish-held area of northern Syria near Manbij. Turkish-backed Syrian opposition fighters said they have started moving along with Turkish troops to front-line positions near the town as a show of readiness.

A statement released by the rebels said they are ready to "begin military operations to liberate the city in response to calls by our people in the city of Manbij."

Turkish news agency IHA showed video of at least 50 tanks arriving at a command post in Sanliurfa province early Saturday. The province borders Kurdish-held areas east of the Euphrates river in Syria.

The Russian side was represented in Saturday's talks by Foreign Minister Lavrov, Defence Minister Shoigu, and Kremlin foreign affairs aide Yuri Ushakov. The Turkish delegation includes Foreign Minister Mevlut Cavusoglu, presidential spokesman Ibrahim Kalin, intelligence chief Hakan Fidan and Defence Minister Hulusi Akar.

Kremlin spokesman Dmitry Peskov told reporters in Moscow on Saturday that, in addition to the foreign and defence ministers of each country, the meeting was attended by intelligence chiefs from both sides.

Presidents Vladimir Putin and Recep Tayyip Erdogan did not attend the meeting. Peskov said the two would later schedule a separate meeting.

In Syria, opposition activists said the head of a local council allied with the Kurds was assassinated in the eastern province of Deir el-Zour. The Britain-based Syrian Observatory for Human Rights said Marwan Fatih, head of the Deir el-Zour Council, was shot dead in the province by unknown assailants. The activist collective DeirEzzor24 said he was killed when a roadside bomb exploded on the highway linking the cities of Deir el-Zour and Hassakeh in the northeast.