WASHINGTON — The US and Russia have yet to finalize an agreement on coordinated efforts in Syria, with Pentagon spokesman Peter Cook warning Monday that the clock is running on the window for those conversations.

"Contrary to recent claims, we have not finalized plans with Russia on potential coordinated efforts. Serious issues must first be resolved before we can implement the steps [Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov] discussed in Moscow last month," Cook said.

"We are not there yet and the regime and Russian's recent actions only make it harder to consider any potential coordination," he added.

Kerry and Lavrov are scheduled for another round of talks starting Aug 26 in Geneva, with the goal of setting up some sort of intelligence sharing agreement in order to coordinate strikes against the Islamic State group, commonly known as ISIS or ISIL.

However, those conversations have become entangled with increased fighting in Aleppo, as well as an incident last week where US fighters were scrambled to intercept Syrian jets that were bombing near US forces.

"The United States remains engaged with Russia on all of these issues, but as our colleagues at the State Department have made clear, we will to commit indefinitely to discussions that do not lead to results," Cook said.

Later asked if there was a set time when the Pentagon would seek to cut off discussions with Russia, Cook demurred, saying "we’re not going to put a calendar deadline on it… at some point, fi we don’t see progress, there’s not going to be a resolution here."

The spokesman also declined to discuss what a Plan B might be if the talks break down between the US and Russia.

Speaking to reporters July 25, Secretary of Defense Ash Carter said the conversations with Russia are based on necessity, rather than trust.

"They're not based on trust," Carter said then. "They're based on a transaction and on mutual interest to the extent — and when and as we're able to identify that with the Russians.

"To the extent that Russia can align with US interests, we work with them as has been the case in Iran, North Korea and other places where US and Russian interests have aligned," Carter added at the time. "It's the alignment of those interests that Secretary Kerry's exploring. That's what it's about."

Aaron Mehta was deputy editor and senior Pentagon correspondent for Defense News, covering policy, strategy and acquisition at the highest levels of the Defense Department and its international partners.

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