Washington (CNN) Vermont Senator and potential presidential contender Bernie Sanders is calling on Democratic front-runner Hillary Clinton "to be clear" on President Barack Obama's trade policy.

At a protest just outside the U.S. Trade Representative's Office near the White House on Monday, Sanders blasted Obama's proposals for fast-track trade promotional authority and the Trans-Pacific Partnership that is aimed at opening up new markets across Asia.

"We want a congress that stands ... not for corporate America and the billionaire class," Sanders told the hundreds of protesters gathered for the demonstration which featured a Trojan horse bearing the letters "TPP."

Asked about Hillary Clinton's past support for the Pacific trade deal, Sanders unloaded on the former Secretary of State.

"She's going to have to be clear. It's not a question of watching this. You're going to have determine which side are you on? Are you on the side of working people who would suffer as a result of this disastrous trade agreement, and seeing their jobs go to China or Mexico, or are you on the side of corporate America? It's not a very difficult choice," Sanders said.

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