Russia's top diplomat called Sunday for the immediate closure of a desert camp near Syria's border with Jordan housing tens of thousands of displaced people in dire conditions.

Speaking during a visit to Amman, Sergei Lavrov called for the Rukban camp to be closed "as soon as possible" and slammed a "de facto occupation" by American forces at a nearby garrison.

Nearly 50,000 Syrians live at the camp near the Al-Tanf base used by the U.S.-led coalition fighting the Daesh.

"According to U.N. observers who visited the camp, most of the displaced people there want to return home, including to territories controlled by the Syrian government," Lavrov said.

"It is necessary to stop the efforts preventing their freedom. I can say this because they do not feel free in this camp," he added.

The Syrian regime and its key backer Russia said in February they had opened corridors out of the camp, calling on residents to leave.

Two weeks later, the U.N. said no civilians were believed to have left, for fears over their safety.

Conditions inside the settlement are dire, with many surviving on just one simple meal a day, often bread and olive oil or yogurt, according to one resident.

Speaking alongside his Jordanian counterpart Ayman Safadi, Lavrov said Moscow was ready to discuss "all steps needed" to help people leave Rukban.

"The most simple and effective solution would be to end the American occupation," he said.

He said the U.S. had "unilaterally announced some sort of security zone in the area" and had "refused to discuss closing the camp."

U.S. President Donald Trump announced in December that he would withdraw American troops from Syria.

But his National Security Adviser John Bolton said the following month that some forces could remain to the al-Tanf garrison as part of efforts to counter the presence of Iran, the Syrian regime's other main backer.