National security adviser H.R. McMaster has touted the ceasefire set to take effect in southwest Syria on Sunday as an "important step" in the effort to combat terrorism in the region.

"The United States remains committed to defeating ISIS, helping to end the conflict in Syria, reducing suffering, and enabling people to return to their homes. This agreement is an important step toward these common goals," McMaster said in a statement.

The U.S. has supported various rebel groups during the country's civil war, while Russia has sided with the regime of President Bashar al-Assad.

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A U.S. Navy aircraft shot down a Syrian warplane in the southern part of Syria in June after the U.S.-supported Syrian Democratic Forces (SDF) reportedly came under attack from pro-Assad forces.

However, the U.S. and Russia share a common enemy in the Islamic State in Iraq and Syria (ISIS).

Secretary of State Rex Tillerson on Friday called the ceasefire effort the "first indication of the U.S. and Russia being able to work together in Syria," according to a Bloomberg reporter.

"This is our 1st indication of the US and Russia being able to work together in Syria," US Sec of State Rex Tillerson tells US reporters. https://t.co/pDdyPPJcci — Jennifer Jacobs (@JenniferJJacobs) July 7, 2017

The ceasefire will take effect on Sunday at noon Damascus time.