Secretary of State John Kerry admitted Monday that Russia has failed to meet his Aug. 1 deadline for playing a more constructive role in Syria, and warned that he now sees Russia's actions in Syria as "very troubling."

Kerry warned Russia back in May that it has to help the U.S. and other allies start moving Syria toward a political transition by today. That date was still months after a United Nations-brokered cease-fire was supposed to take effect in Syria.

But on the day of the deadline, Kerry acknowledged in Washington that Russia has failed to meet his expectation. He said ongoing fighting in Syria has made it "impossible" to sit down and negotiate, and said the last several months have been filled with unsuccessful efforts to enforce the cease-fire despite Russia's ongoing military action there.

"It is critical, obviously, that Russia restrain both itself and the [Bashar] Assad regime from conducting offensive operations, just as it is our responsibility to get the opposition to refrain from engaging in those operations," Kerry said.

"Now, my hope is that we can arrive at that," he said. "If we can't, nobody is going to sit around and allow this pretense to continue."

"These are important days to determine whether or not Russia and the Assad regime are going to live up to the U.N., live up to the cycle or not," Kerry added. "And the evidence thus far is very, very troubling to everybody."

"We will see in the course of the next hours, few days, whether or not that dynamic can be changed," he concluded. "But it's very complicated when both parties on the ground want to fight rather than live up to the obligation of the U.N. Security Council resolution."

Kerry didn't explain what might come next now that Russia seems to have ignored his deadline. But one outcome could be more hurdles to reaching a U.S.-Russia agreement on military cooperation in Syria.

Just last week, Kerry hinted there was progress in the effort to find a framework deal with Russia, and said he was hoping to announce something more concrete this week.

But he had no comment on whether that's a possibility now.