U.S. Secretary of State John Kerry has urged Russia and Syrian President Bashar al-Assad's regime to respect a shaky cease-fire, warning that Washington's patience is running out.
"Russia needs to understand that our patience is not infinite, in fact it is very limited with whether or not Assad is going to be held accountable," Kerry said on June 15 after a meeting with Iranian Foreign Minister Mohammad Javad Zarif in Oslo, Norway.
"We also are prepared to hold accountable members of the opposition" who have been involved in continuing violence, Kerry said.
Kerry insisted there was a need for a "genuine cessation of hostilities" in Syria to allow humanitarian aid deliveries and pave the way for transition talks.
"I do believe the conversation I had with Zarif indicates to me possibilities for how this could be achieved," he added.
Russia and Iran are Assad's key diplomatic and military allies.
In February, a cessation of hostilities went into effect in Syria. The truce later crumbled with the Syrian opposition and Damascus trading blame for its collapse.