Representative Mike Rogers, chairman of the House Intelligence Committee, said Russian authorities were clearly concerned about security at the Winter Games, having moved 30,000 troops to the area amid bombings and disrupted plots.
"But we don't seem to be getting all of the information we need to protect our athletes in the games," he said on CNN's "State of the Union."
Rogers, a Republican, said the Russians' unwillingness to share information with US intelligence was "a departure of cooperation that is very concerning to me."
"Are the terrorist groups who have had some success, are they still plotting?" Rogers continued.
"There's a missing gap and you never want that when you're going to something I think as important as the Olympic Games," he said.
The Games open February 7 at Sochi, a resort city on the Black Sea coast.