Rohrabacher said earlier this month that one reason for his visit is to examine how the U.S. and Russia might have cooperated better on the Tsarnaev brothers, who are suspected of detonating homemade bombs at the finish line of the Boston Marathon in April.

Russia warned the U.S. about the two brothers, but that warning didn't translate into a concerted effort in the U.S. to watch them more closely before the bombing. But the delegation is also looking to find out why Russia didn't respond to later U.S. requests for information.

Before leaving, Rohrabacher's office said questions about the Boston bombing were just part of a trip aimed at increasing cooperation between the two countries, and Rohrabacher confirmed that dual mission from Russia on Wednesday.

"Overall, the purpose of this trip is to examine the information provided to us on the Boston bombers and further the cause of Russian-American cooperation on not only issues of national security but also aerospace," he said.

Rohrabacher said the delegation has met with officials at the "highest levels of the Russian government" to improve relations and discuss "how to best meet the challenge posed by radical Islamic terrorism."

"Over the last two decades, the Russians too have been victims of Islamic terrorism," he said. "Today the U.S. shares a common enemy of radical Islamic terrorism as the number one challenge to our country followed closely by a hostile and adversarial China."

Also on the trip are Reps. Michele BachmannMichele Marie BachmannBachmann won't run for Franken's Senate seat because she did not hear a 'call from God' Billboard from ‘God’ tells Michele Bachmann not to run for Senate Pawlenty opts out of Senate run in Minnesota MORE (R-Minn.), Steve Cohen (D-Tenn.), Paul Cook (R-Calif.), Bill Keating (D-Mass.) and Steve King (R-Iowa).