WATCH: Joe Biden suggests Trump's being blackmailed by Putin

Former Vice President Joe Biden suggested President Donald Trump may be compromised by Russia and its president.

Biden sat down Thursday for an interview with MSNBC's Andrea Mitchell, who asked the former vice president why Trump was "so reluctant to take on Vladimir Putin."

"Look, you know, I want to give every American, including the president, the benefit of the doubt, but I can't fathom any reason other than he is concerned of what Putin might say or do, or what information he may or may not have," Biden said.

He then warned the Trump administration was not doing enough to stop the Russian from interfering with the next election.

"But look, unrelated to the whole issue of whether or not there's collusion, separate and apart from all that, it's necessary for us to stem this problem," he said. "It's necessary for us to corral the Russians."