The United States says it is suspending talks with Russia on trying to end the violence in Syria and accused Moscow of not living up to its commitments under a cease-fire agreement.
In an statement on October 3, U.S. State Department spokesman John Kirby accused Russia and its ally Syria of stepping up attacks on civilian areas.
"Russia and the Syrian regime have chosen to pursue a military course, inconsistent with the Cessation of Hostilities, as demonstrated by their intensified attacks against civilian areas, targeting of critical infrastructure such as hospitals, and preventing humanitarian aid from reaching civilians in need," Kirby said.
"This is not a decision that was taken lightly," Kirby said.
Russia's Foreign Ministry said it regretted the decision by the United States to suspend talks aimed at ending the violence in Syria, saying Washington was trying to shift responsibility for the failure onto Moscow.
"We regret this decision by Washington," spokeswoman Maria Zakharova was quoted as saying on October 3 by Russian news agencies.
Zakharova added that Washington had not fulfilled key aspects of a cease-fire deal brokered with Moscow.
Russia had taken steps in recent days to sustain that deal, Zakharova said.
A State Department spokesman, Elizabeth Trudeau, said that despite the suspension of talks, U.S. and Russian military commanders remained in contact in an effort to avoid accidents, or outright conflict, between the two countries' air forces flying in Syrian airspace.
As part of the suspension, the United States said it was withdrawing personnel that it had dispatched in anticipation of the possible creation of a joint U.S.-Russian center. That center was to have coordinated military cooperation and intelligence if the cease-fire had taken hold.
The announcement came just hours after Russian President Vladimir Putin suspended a 16-year-old agreement on the disposal of U.S. and Russian weapons-grade plutonium stocks, a move that further underscored rising tensions between Washington and Moscow.