John Brennan also said the "ISIL threat demands" an "unprecedented level of cooperation" among the international intelligence community, mere hours before the Obama administration announced new rules easing the sharing of intelligence with France in the wake of the Nov. 13 Paris attacks.
Brennan said he has been having ongoing conversations with "my Russian counterpart" over the last year, including several since Russian forces began operating in Syria, the latest flashpoint between the US and the government of Russian President Vladimir Putin.
Those conversations have largely centered on the flow of potential terrorists between Russia and ISIS-controlled territory, a "very real concern" for the Russians, Brennan said. He added that there are between 2,000 and 3,000 Russians, largely from the Caucuses, that are active in the Syria and Iraq region, as well as a handful of Chechens who are highly ranked within ISIS.
"So we've been exchanging information," Brennan said. "I think it needs to be enhanced. 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.
"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," he added.
Hours after Brennan's comments, the Obama administration announced a loosening of rules constraining intelligence-sharing with France.
"Secretary of Defense Ash Carter and Director of National Intelligence Jim Clapper have provided new instructions that will enable U.S. military personnel to more easily share operational planning information and intelligence with our French counterparts on a range of shared challenges to the fullest extent allowed by existing law and policy," Pentagon Press Secretary Peter Cook said in a statement.
French President Francois Hollande also announced today that his government would be opening trilateral talks with the US and Russia in order to "join our forces" against ISIS. If those talks are fruitful, it could mean Brennan may get his wish for greater information-sharing in the near future.
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.