"While Russia remains an adversary, we would put American lies at greater risk if we ignored opportunities to work with the Russian services in the fight against terrorism," Pompeo said in his letter, which came in response to Schumer's criticism of a recent meeting between US and Russian intelligence officials in Washington.
Pompeo also said Moscow and Washington maintain collaboration on aviation security and on preventing foreign fighters from going back to both Russia and the United States.
Speaking about the recent meeting between US and Russia intelligence officers, Pompeo said the sides addressed difficult topics there and were forthcoming about all of their concerns.
"You and the American people should rest assured that we cover very difficult subjects in which American and Russian interests do not align. Neither side is bashful about raising concerns relating to our intelligence relationships and the interests of our respective nations," Pompeo added.
According to the Washington Post, Pompeo met with Head of the Russian Foreign Intelligence Service (SVR) Sergei Naryshkin and Federal Security Service (FSB) chief Alexander Bortnikov in the US capital.