Oren Dorell, and Kim Hjelmgaard

USA TODAY

A United Nations aid convoy was struck while trying to reach civilians in Syria Monday, as the country's military declared an end to a week-old cease-fire brokered by Russia and the United States.

The military's announcement followed violations on all sides, including a U.S.-led coalition airstrike on Saturday that mistakenly killed dozens of Syrian soldiers.

The U.N. said an aid convoy was hit Monday in Aleppo province. The Syrian Observatory for Human Rights, a London-based monitoring group, said at least 32 people — including 12 in a convoy of aid trucks — were killed in airstrikes on parts of Aleppo and areas to the west held by rebel forces.

Syria’s military earlier blamed rebel groups for undermining the cease-fire that aimed to bring the country's bloody five-year civil war to an end.

State Department spokesman John Kirby said under terms of the truce agreement, Russia "is responsible for the Syrian regime's compliance, so we expect Russia to clarify their position."

He said the United States is prepared to extend the cease-fire, "while working to strengthen it and expand deliveries of assistance."

The State Department criticized Syrian forces and their Russian allies for repeatedly targeting aid convoys.

Brief cease-fire for Aleppo until 'nightmare of war' returns in Syria

Secretary of State John Kerry in New York called on Russia to restrain Syrian President Bashar Assad and said it is too soon to say whether the cease-fire is dead.

"The important thing is the Russians need to control Assad, who evidently is indiscriminately bombing, including of humanitarian convoys," Kerry said.

The Syrian military said in its statement that “armed terrorist groups” repeatedly violated the cease-fire that went into effect on Sept. 12, the Associated Press reported. The military said the armed groups also took advantage of the truce to mobilize and arm themselves while attacking government-held areas.

Rebel groups countered by accusing the Syrian government of violating the cease-fire, the AP said. The United Nations said the Syrian government has obstructed the delivery of aid, a key component of the deal.

U.S. airstrike threatens to derail week-old Syrian cease-fire

As part of the truce agreement, Russia and the United States had said if the cease-fire lasted for seven days they would begin cooperating on military operations against the Islamic State and the Jabhat Fatah al-Sham — previously known as Nusra Front — in Syria.

Russian-U.S. cooperation now appears in jeopardy following Syrian government attacks on rebel-held neighborhoods over the weekend, the inability of aid convoys to reach besieged areas in Aleppo and the apparently mistaken airstrikes on Saturday that killed at least 62 Syrian troops and wounded 100 more.

The Pentagon expressed regret for the airstrikes, which it said were meant to target Islamic State militants battling the Syrian troops. Instead, the militants gained an advantage from the airstrikes that included Australian, British and Danish warplanes.

Lt. Gen. Sergei Rudskoi of the Russian military blamed Washington for sabotaging the deal, although he stopped short of saying the cease-fire and partnership was being abandoned. Rudskoi said repeated violations by opposition forces meant it was "meaningless for Syrian government forces to unilaterally observe the cease-fire."

Moscow supports Assad in his battle to retain power, while the Obama administration wants him to step aside because of alleged atrocities against his own people.