"I think it's just irresponsible for Democrats to sign off on a six-year fast-track deal," Warren said on a conference call organized by progressive groups, including Democracy For America and MoveOn.org.

The administration is on the verge of getting Congress to pass Trade Promotion Authority (TPA) on Friday, which would give the president expanded powers to negotiate trade deals.

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It's commonly referred to as "fast-track" authority because it would allow the president to negotiate a deal with other countries and send the deal through Congress without allowing lawmakers to attach amendments.

Progressives like Warren have lobbied heavily against Obama, largely out of concern big businesses will use the trade deals to weaken regulations. Some Tea Party Republicans also oppose giving Obama expanded executive powers.

But the administration and moderate Democrats and Republicans support it, arguing the deal will help boost economic growth while supporting updated worker protections.

With Obama poised for a major win on Friday, Warren isn't backing down.

"Even when the odds are against you, sometimes you need to stand up and fight," Warren said. "Never give up on holding Wall Street accountable. I repeat — never."