U.S. Sen. Martin Heinrich announced Friday that he opposes a fast track for the Trans-Pacific Partnership, or TPP, the latest in a line of controversial trade agreements.

Heinrich, a Democrat, is going against President Barack Obama in opposing the quick approval of the treaty. The TPP is a rare occasion where Republicans and Obama are on the same page and the deal is expected to get a Senate vote.

“They call that Trade Promotion Authority or TPA, but it’s really just re-branded ‘Fast Track’ legislation designed to allow trade deals to be pushed through Congress with little or no debate,” Heinrich wrote on Facebook late last week.

Heinrich outlined some of his concerns with possibilities of what could be in the treaty including, saying that changes could not be made if the quick approval makes it through Congress.

What would that mean? No amendments to make sure our competitors cannot manipulate their currency value to the detriment of American workers and American small businesses. No amendments to ensure that we don’t cede our sovereignty to international courts or “arbitration panels” who can overturn the very laws and regulations New Mexicans rely on for fair labor practices, public health and clean water.

The treaty would include trade between the United States and 11 Pacific Rim nations. China is not included among those countries.

Much of the opposition to TPP has come from Obama’s left.

Liberal firebrand Elizabeth Warren, a Democratic U.S. Senator from Massachusetts, has publicly clashed with the Obama administration.

Obama riled up opponents of TPP with statements he made Friday, after Heinrich released his opposition to the fast track.

The left-leaning Economic Policy Institute says that the treaty would hurt American workers by holding wages down, especially for workers without college degrees.

Of course, all of the criticisms are not based on a full picture of what the TPP will actually look like; the treaty is not public yet and has largely been kept secret. What is known about the proposed agreement is largely as a result of leaks.

Heinrich mentioned this secrecy in his Facebook post.

“Unfortunately, before I ever see the details of TPP, and before the American public gets to see the details of the deal, I am being asked to give away any chance I would have as a U.S. Senator to change it, make it better, or fix what could be fatal flaws,” Heinrich said.

Members of Congress have been briefed on the deal but have been barred from publicly discussing the details.

Progressive groups are preparing a large ad campaign opposing the deal.

The opposition doesn’t all come from the left. Some conservatives have said the deal would open the door to “amnesty.”

This view is more of a fringe concern, and Republicans are considered likely to back the trade deal.