The two countries are the chief architects of the fragile truce. They're using a joint statement to show they're still committed to holding the truce together and resuming peace talks to end Syria's civil war.
The US and Russia say they are also committed to developing a "shared understanding" of where the Islamic State and the al Qaida-linked Nusra Front hold territory.
The groups are excluded from the cease-fire but are fighting alongside Western-backed rebels, complicating efforts to enforce the truce.