The top diplomats of Russia and the United States are meeting in Geneva to discuss the Syria civil war, the Ukraine crisis and other issues.

U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov were meeting as part of a new U.S. bid to enlist Russia as a partner in Syria as the fighting on the ground becomes more volatile with the introduction of Turkish ground forces.

The U.N. has been clamoring for a 48-hour cease-fire in beleaguered Aleppo so humanitarian aid can be shipped into the city.

Asked by a reporter to describe the main impediment to a nationwide ceasefire in Syria, Lavrov said: "I don't want to spoil the atmosphere for the negotiations."

Kerry was to meet with the U.N. envoy for Syria later Friday.