[UPDATE] 6:03 a.m.
The High Negotiations Committee (HNC), an umbrella group that opposes Syria, on Saturday welcomed the deal, saying it hoped it would bring relief to civilians.
"When the cessation of hostilities was installed in February, the Opposition -- 100 groups -- respected it. It was violated by the regime," Bassma Kodmani, a member of HNC said in a statement. "So a return to a cessation of hostilities has been our demand."
"We are absolutely in favor of it."
The U.S. and Russia confirmed early Saturday morning in Geneva that negotiations for a cease-fire in Syria and a military partnership against ISIS and al-Qaida have been successful.
The cease-fire will begin at sundown on Sep.12 and will bring more than five years of open conflict to a temporary end. Secretary of State John Kerry has said that this agreement could be a potential turning point in a conflict that has claimed the lives of as many as 500,000 people.
The agreement will also see two nations form a counterterrorism alliance designed to combat ISIS and al-Qaida. That part of the agreement will kick in after the cease-fire stays in effect uninterrupted for a week. Only then will the two governments start to share intelligence and coordinate their efforts.
This doesn't mean the two nations are necessarily happy with each other. The Obama administration has criticized Russia for engaging in strategies it believes are designed to keep Syrian President Bashar al-Assad.
On the other hand, Russia isn't thrilled that America has been supporting rebel forces that have intermingled with groups fighting in an area in which its engaged.
The Associated Press contributed to this report.