The United States and Russia said early Saturday in Geneva they had reached a landmark agreement that would lead to a cease-fire in the five-year-old Syrian civil war and pave the way for broader military cooperation in the battle against the Islamic State and al-Qaeda terrorists.
Secretary of State John Kerry called the deal a potential "turning point" in the bloody conflict, which has caused hundreds of thousands of deaths and forced millions to flee their homes. Kerry and Russian Foreign Minister Sergey Lavrov announced the agreement in Geneva, Switzerland where negotiators hammered out the deal.
The cease-fire is set to begin at sundown on Monday. It is seen as a first step in what could become a broader military pact between Russia and the United States that has so far remained elusive.
There are still formidable obstacles in the way of carrying out the agreement. Hundreds of factions are fighting in Syria and getting them all to cooperate will be a challenge. A previous ceasefire agreement in Syria collapsed.
This deal appears more ambitious, since it includes an agreement to seek broader military cooperation between Russia and the United States if the ceasefire holds.
The Pentagon said that a "cessation of hostilities" would have to hold for seven days before the broader military cooperation would go into effect.
"We will be watching closely the implementation of this understanding in the days ahead," Pentagon Press Secretary Peter Cook said in a statement. The Pentagon has been wary of Russian military actions in Syria.
Lavrov said Syrian President Bashar al-Assad is willing to comply with the agreement, according to the Associated Press.
Russia and the United States are both conducting military operations in Syria. The Pentagon is backing local ground forces and conducting airstrikes against the Islamic State.
Russia is also conducting airstrikes, but Washington has accused it of carrying out operations aimed at propping up the Assad regime by striking members of U.S.-back moderate opponents of the Syrian president. The United States wants Assad to step down because of his brutal attacks on civilians with chemical weapons and other armaments.
Russia and the United States have agreed to hold regular talks aimed at ensuring aircraft remain at safe distances from each other, but are not cooperating on military operations.
A broad agreement to cooperate could mean the two sides would eventually share intelligence and agree on which targets to strike.