US President Donald Trump has confirmed that a ceasefire agreement in northern Syria between Ankara and the SDF is holding up very well.

During a meeting with his Turkish counterpart Recep Tayyip Erdogan at the White House, he said Washington had left a military force in northern Syria only to secure oil fields.

Trump also thanked his Turkish counterpart for the actions taken by his country on the Turkish-Syrian border, stressing that Ankara has been able to arrest more than 100 fighters from the state organization "terrorist".

"We have concluded an agreement with Turkey on a ceasefire in northern Syria, and this agreement is still in effect and I am grateful for that," he said.

"I understand Turkey's problem with the Kurds, and there are many Turks who have lost their lives in the region. We have to do something."

On the other hand, Trump confirmed that he would discuss with Erdogan the Russian missile system "S400" purchased by Turkey, and the US fighter program "F-35".

He said his country seeks to boost its trade with Ankara, expressing his belief that the volume of trade exchange between the two countries could be increased from 20 billion to 100 billion dollars.

Relations between Washington and Ankara reached a crisis point last month over Syria, after Erdogan began a cross-border incursion to target Washington's Kurdish allies and prevent what Turkey calls a "terrorist corridor" on its border.

Washington was also troubled earlier this year by Turkey's purchase of Russia's S400 defense system, which the United States says is incompatible with NATO equipment, including F-35 fighter jets.