US and Russia Agree on Terms for Syria Cease-Fire

— -- For the second time this month, the U.S. and Russia are attempting to broker a cease-fire inside Syria. In a joint statement released today, the two countries announced their agreement for a "cessation of hostilities" beginning this Saturday.

President Barack Obama and Russian President Vladimir Putin spoke by phone today to talk about the plan, the White House said. In that call, President Obama said the focus now shifts to making sure the Syrian regime, the armed opposition and all other parties respond in a positive manner, according to a statement from press secretary Josh Earnest.

The agreed-upon terms follow a previous commitment to cease hostilities by last Friday that failed to come to fruition. Terrorist groups ISIS and al-Nusra would be excluded from the truce, while all other warring parties are expected to sign on. The architects of these talks, Russia and the U.S., seen as proxies aligned with opposing forces, would not be required to end their aerial bombing campaigns.

"I am gratified to see the final arrangements concluded today for a cessation of hostilities in Syria and call on all parties to accept and fully comply with its terms," Secretary of State John Kerry said in a statement today.

"If implemented and adhered to," he continued, "this cessation will not only lead to a decline in violence, but also continue to expand the delivery of urgently needed humanitarian supplies to besieged areas and support a political transition to a government that is responsive to the desires of the Syrian people."

In its own statement, the Russian Foreign Ministry said Foreign Minister Sergey Lavrov and Secretary Kerry spoke twice by telephone on Sunday evening and during the course of their conversations agreed on the parameters for the cease-fire.

While Russia claims it can use its influence to convince Syrian President Bashar Assad to end his military campaign, the dictator seems unwilling to relent. “There is no such thing as a cease-fire," Syria's information minister, Omran al-Zoubi, told the Wall Street Journal today. “The Syrian army is coming and it will enter every town in Syria.”

In Jordan yesterday, Secretary Kerry warned any groups who may choose not to sign on to the cease-fire. "Will every single party agree automatically? Not necessarily," Kerry said. "But we are very clear that if you don’t choose to be part of it, then you are choosing to perhaps make yourself a target. And so, there is a stark choice for everybody here."

Kerry said the purpose of waiting a week is to get those parties to commit. A similar plan was executed the first time around, but hostilities raged on as the deadline for a cease-fire passed last Friday.

Over the weekend, the death toll rose to 155 following bombings that hit Damascus and Homs on Sunday, according to the Syrian Observatory for Human Rights. ISIS claimed responsibility for the six explosions that hit the two cities targeting predominantly Shiite and Alawite neighborhoods.

ABC News Foreign Correspondent, Alexander Marquardt, contributed to this report.