Vladimir Putin and Barack Obama have held a telephone conversation about the Syrian war and the unresolved conflict in Ukraine.

A White House statement said the conversation between the Russian and U.S. presidents occurred on Saturday and a Kremlin statement said it took place at Washington's initiative, but didn't specify when it occurred.

On Syria, the Kremlin statement said "both sides gave a positive assessment of the results of the meeting of the International Syrian Support Group in Munich on Feb. 11-12, confirmed the principles and provisions of the U.N. Security Council Resolution 2254 both in terms of humanitarian aspects and to develop modalities for the cease-fire, and in promoting the launch of a real political process."

Putin stressed the importance of creating a "common front against terrorism" and establishing a working relationship between the Pentagon and the Russian Defense Ministry, it said.

The White House said Obama "emphasized the importance now of Russia playing a constructive role by ceasing its air campaign against moderate opposition forces in Syria." Russia says the airstrikes it began on Sept. 30 are aimed at extremist groups, but there are wide claims from the West that Russia is targeting rebels fighting the forces of Syrian President Bashar Assad, a longtime Moscow ally.

On Ukraine, Obama urged Russia-backed rebels in eastern Ukraine to fulfill their obligations under a peace deal signed a year ago, while Putin made a similar call for the Ukrainian government to live up to its part of the agreement.