Sen. Elizabeth Warren Elizabeth WarrenNo new taxes for the ultra rich — fix bad tax policy instead Democrats back away from quick reversal of Trump tax cuts It's time for newspapers to stop endorsing presidential candidates MORE (D-Mass.) is pushing her Senate colleagues to reject a Pacific Rim trade deal that's considered a key pillar of President Obama's second term.

"I hope Congress will use its constitutional authority to stop this deal before it makes things even worse and even more dangerous for America's hardest-working families," Warren said Tuesday.

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She added that the agreement "would tilt the playing field even more in favor of a big multinational corporations and against working families."

Warren's comments come as the countries involved in the Trans-Pacific Partnership (TPP) are expected to sign the agreement on Wednesday.

The Massachusetts lawmaker was one of 38 senators who voted agains t a bill last year allowing the president to "fast-track" trade agreements through Congress on a simple majority vote, with senators unable to amend the deals.

The administration argued that the fast-track bill was crucial to finishing TPP negotiations. But the months-long trade battle has divided Democrats, pitting liberal senators publicly against the president.

Warren added Tuesday that Congress's inability to amend the TPP is why she's opposing it, saying lawmakers "won't have a chance to strip out any of the worst provisions."

Obama's trade deal has come under fire from lawmakers in both parties in Congress, including both Senate Majority Leader Mitch McConnell (R-Ky.) and Minority Leader Harry Reid (D-Nev.).

McConnell suggested the Obama administration shouldn't try to get the agreement through Congress until after the November election, which got quick pushback from the White House.

Meanwhile, Reid has been vocal about his opposition to the agreement and pledged that he won't help Obama get it through the Senate.

Asked last month whether the president brought up the trade agreement during a White House meeting, Reid replied: "Briefly. When I'm around, that's a good way to talk about it — briefly."