Washington (CNN) Vermont Sen. Bernie Sanders said he'll decide whether to run for president "very shortly, within a couple of weeks" in an interview with CNN's Wolf Blitzer on Thursday, but admitted fundraising is "absolutely " his biggest challenge.

But Sanders already sounded like a presidential contender, offering somewhat of a backhanded compliment for the only declared Democrat in the race, former Secretary of State Hillary Clinton.

"I happen to like Hillary Clinton very much," he said. "And she is far preferable to any of the Republican candidates, let's be clear about that."

JUST WATCHED Sen. Sanders on 2016: We'll see Replay More Videos ... MUST WATCH Sen. Sanders on 2016: We'll see 02:54

Sanders, who has emerged as a prominent progressive Clinton antagonist as he contemplates a potential bid, said that the nation needs a "political revolution" of working-class Americans looking to take back control of the government from billionaires.

Read More