Turkish President Recep Tayyip Erdogan met UN Secretary-General Antonio Guterres at the organization's headquarters in New York on Monday.
The closed door meeting came a day before Erdogan's address to the General Assembly's 73rd session.
The UN said Guterres "commended the excellent UN-Turkish cooperation, including in support of Turkey's hosting of more than 3.5 million refugees," following the bilateral.
"The Secretary-General and the President discussed the situation in Syria, with the Secretary-General welcoming the agreement reached on 17 September to create a demilitarized zone in Idlib," the UN said in a statement.
Turkey and Russia also signed a memorandum of understanding on that date calling for the "stabilization" of Idlib's de-escalation zone, in which acts of aggression are expressly prohibited.
Under the pact, opposition groups in Idlib will remain in areas where they are already present, while Russia and Turkey will do joint patrols in the area to head off renewed fighting.
The theme of this year's general assembly meetings is Making the United Nations Relevant to All People: Global Leadership and Shared Responsibilities for Peaceful, Equitable and Sustainable Societies.
Erdogan's schedule in New York runs through Wednesday.
