In another sign that the acrimonious relationship between Moscow and Washington might be changing under the force of events, the head of the CIA said Monday he wants to see greater cooperation between the two countries' spy agencies to prevent further terrorist attacks by groups like the Islamic State, Defense News reported. U.S. President Barack Obama and Russian President Vladimir Putin held an informal talk Sunday at the G-20 summit in Turkey after the bloody terrorist attacks in Paris.

“So we’ve been exchanging information. I think it needs to be enhanced,” CIA Director John Brennan said, speaking in Washington. “But I am determined to continue to work with my Russian counterparts, because of the importance that I think we each can bring to this issue, in terms of our insights, our information, our data and sharing.”

Brennan said the threat posed by ISIS demanded increased cooperation. He said conversations with Russian counterparts have focused on the movement of terrorists, especially from southern Russia’s Caucasus region. Russia has long faced terrorism, with several major attacks over the last 15 years.

Greater intelligence sharing would signal a major departure in American policy toward Russia. The U.S. and EU applied harsh economic sanctions against Russia following the annexation of Crimea from Ukraine in March 2014. The ensuing conflict in eastern Ukraine that began in April 2014 has taken the lives of more than 8,000 people and displaced more than 1.4 million people. Russia has denied any direct role in the conflict that has pitted Ukrainian government forces against Russian-backed separatists.

Russia launched airstrikes in Syria at the end of September with Western leaders accusing the Kremlin of also targeting opposition groups in order to support its ally, Syrian President Bashar Assad. The U.S. has long called for Assad's removal.

“Irrespective of disagreements of policy over Syria, I am determined to work with other country services the best I can in order to prevent successful terrorist attacks,” Brennan said.

U.S. officials have been careful in describing cooperation with Russia in Syria, saying a three-minute aircraft exercise at the beginning of November was only a "communications test."

Russian security experts told International Business Times that following the terror attacks in Paris, Putin could use Russia’s role in the Middle East as leverage regarding his isolation over Ukraine.

“Russia has created a bargaining chip -- we’ll be nice to you in the Middle East if you’ll be nice to us in Ukraine,” said Mark Galeotti, a professor in global affairs at New York University with a specialty in Russian security affairs.

Ukrainian authorities said Monday they were considering returning artillery to the front lines in the Donbass region after fighting increased, Reuters reported. Both the Ukrainian government and rebels had withdrawn artillery as part of a ceasefire agreement.