The United States announced it is suspending efforts to revive a cease-fire in Syria, blaming Russia's support for a new round of airstrikes in the city of Aleppo.

As NPR's Michele Kelemen reports,

"The U.S. was offering to cooperate with Russia in the fight against extremists in Syria, but only if Russia used its influence with Bashar Assad's regime in Damascus to ground the Syrian air force. The State Department says Russia failed to live up to its commitment, so the U.S. is suspending the talks. Spokesman John Kirby says the decision was not taken lightly."

In his statement, Kirby said:

"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, including through the September 19 attack on a humanitarian aid convoy."

As The New York Times reports, the announcement comes less than a week after Secretary of State John Kerry warned Russia that the cease-fire agreement the two countries reached on Sept. 9 was in jeopardy.

The suspension of the cease-fire talks comes just after another indication of worsening relations with Russia, reports The Washington Post:

"Just hours earlier, the Kremlin announced Russia had suspended participation in a landmark agreement with the United States to dispose of weapons-grade plutonium.A decree issued by President Vladi­mir Putin said the plutonium suspension was the result of U.S. "unfriendly actions," and demanded that Washington reduce its military presence in NATO countries near Russia and cancel all sanctions against it."Copyright 2016 NPR. To see more, visit