US, Russia urge adherence to fragile cease-fire in Syria

U.S. Secretary of State John Kerry, foreground center, attends a meeting on the conflict in Syria in Paris, Monday, May 9, 2016. Representatives of Britain, Germany, Italy, Saudi Arabia, UAE, Qatar, Jordan, Turkey and the EU have also been invited in Paris Monday for a meeting in the presence of the Riad Hijab, head of the Western-backed Syrian opposition coalition, in an effort to re-launch the Syrian peace process.(AP Photo/Christophe Ena) (The Associated Press)

Secretary of State John Kerry, center, attends a meeting on the conflict in Syria in Paris, Monday, May 9, 2016. Representatives of Britain, Germany, Italy, Saudi Arabia, UAE, Qatar, Jordan, Turkey and the EU have also been invited in Paris Monday for a meeting in the presence of the Riad Hijab, head of the Western-backed Syrian opposition coalition, in an effort to relaunch the Syrian peace process.(AP Photo/Christophe Ena) (The Associated Press)

U.S. Secretary of State John Kerry speaks to journalists before a meeting with French Foreign minister Jean-Marc Ayrault, in Paris, Monday, May 9, 2016. Kerry has arrived in Paris for talks on the conflict in Syria. Representatives of Britain, Germany, Italy, Saudi Arabia, UAE, Qatar, Jordan, Turkey and the EU have also been invited in Paris Monday for a meeting in the presence of the Riad Hijab, head of the Western-backed Syrian opposition coalition, in an effort to relaunch the Syrian peace process.(AP Photo/Christophe Ena) (The Associated Press)

The United States and Russia are urging Syria's government and opposition groups to adhere to a revived cease-fire and allow humanitarian aid to flow to critical areas.

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 U.S. 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.

The statement comes as U.S. Secretary of State John Kerry attends a meeting in Paris of nations supporting the opposition.