The chairman of the U.S. Joint Chiefs of Staff spoke on the phone Saturday with a top Russian military official. They discussed developments in Syria, including a Russian-proposed plan for "safe zones" that went into effect on Saturday.

The multi-face plan is one of the more ambitious efforts to end Syria's six-year conflict. The U.S. is watching closely to see if it can successfully take hold.

The deal was signed Thursday by Russia and Iran, who support the Assad regime, and Turkey, who backs the opposition.

Under the agreement, starting Saturday, several so-called "de-escalation zones" will be created. These safe zones would see a halt to all hostilities, including airstrikes, allowing for humanitarian aid to be delivered and for civilians to safely return. There's also a proposal to deploy third-party monitoring forces.

A Russia proposed "safe zone" plan to de-escalate the conflict in Syria went into effect on May 6, 2017. CBS News



Washington says they remain cautious, but support any effort to de-escalate the conflict in Syria -- and there are already reports on the ground of a significant drop in violence.

However, fighting has been reported in some included areas, including this purported regime airstrike in Hama province.

If history is any indicator, forging a peaceful path in Syria won't be easy - opposition leaders have already criticized this agreement as being biased towards the regime.

Several ceasefire deals have previously been agreed since Syria's conflict broke out in 2011, but they have all failed to permanently stem the fighting.