Washington and Moscow support opposing sides in the bloody five-year conflict, which has left 300,000 people dead and forced millions to flee.
The two leaders discussed Syria at closed multilateral meetings but could not reach a deal to ease fighting in the war-torn region.
But in their final face-to-face meeting before Obama leaves office in January next year, they agreed to keep up negotiations over a cease-fire agreement
A senior US administration official said they had a longer-than-expected discussion during a 'constructive' meeting.
It comes as Syrian government troops - backed by Russia - resumed their siege of the city of Aleppo.