The United States and Russia have agreed on plans for a cessation of hostilities in Syria, a move that could pave the way for an expansion of humanitarian aid to besieged cities and set the stage for a resumption of talks on a political transition.

In a joint statement Monday, the U.S. and Russia proposed the cease-fire begin on February 27.

It would apply to all parties in the conflict, with the exception of terrorist groups such as the Islamic State group and al-Qaida-affiliated Jabhat al-Nusra.

The White House said President Barack Obama and Russian President Vladimir Putin spoke by phone Monday to discuss the agreement.

The joint U.S-Russian statement said a “communication hotline” would be established to help promote and sustain a cease-fire and that a working group, would be set up for an exchange of information, if necessary.

“Over the coming days, we will be working to secure commitments from key parties that they will abide by the terms of this cessation,” said Secretary of State John Kerry.

“This is a moment of promise,” he said, but added that fulfillment depended on actions.

The U.S. and Russia are co-chairs of a cease-fire task force that is part of the 17-nation International Syria Support Group.