It’s official, Sander Levin opposes the Pacific Rim trade agreement.

The top Democrat on the House Ways and Means Committee announced Thursday that he is adding his name to the growing list of lawmakers opposed to the deal, further highlighting the growing challenge the Obama administration faces in getting Congress to approve the trade pact this year.

Levin (D-Mich.), who represents a manufacturing-heavy district just north of Detroit, did not rule out supporting the Trans Pacific Partnership in the future if changes are made, but he said the deal does not go far enough to protect workers or prevent cheap Chinese auto parts from flooding the U.S. market. Levin said he raised these issues throughout the negotiating process and is disappointed by the final agreement.

“My position has never been no TPP, my position has been we have to address these very major issues that I outlined a year ago,” Levin said Thursday at a breakfast hosted by the Christian Science Monitor.

The 12-nation trade agreement includes plans for member countries like Vietnam and Malaysia to implement new workers rights protections after the trade deal is ratified. Levin said there is no evidence that these countries are making progress on promises to protect workers who attempt to form unions and increase wages. Levin said he cannot support the deal until there is proof that member nations will follow through.

“If you believe those changes are going to be real they should occur at least in meaningful ways before we vote,” Levin said. “You can’t say a document is going to be worthwhile if the practice today is in total contradiction.”

Levin also opposes a provision in the agreement that would make it easier for member countries to undercut the U.S. auto industry by importing cheap auto parts from China. He said the complex “rules of origin” system could allow TPP member countries to ship Chinese parts to auto plants in Mexico where cars destined for U.S. dealerships are assembled.

“They are very technical but they really matter,” Levin said. “Consumers could find themselves driving TPP cars or trucks with over half of their parts by value made in China or elsewhere and the vehicle itself assembled in Mexico.”

Levin also said the final agreement does not do enough to prevent member countries from devaluing or otherwise manipulating their currency to make investment more attractive.

The number of TPP opponents has grown steadily in recent weeks. House Speaker Paul D. Ryan (R-Wisc.) and Majority Leader Mitch McConnell (R-Ky.) have both said they don’t think the agreements has enough votes to pass in Congress.

Levin voted last year against fast-track negotiating authority for Obama to complete work on the deal and was openly critical of the worker protection provisions. He said he would be open to working with the administration to address his concerns, but it is unlikely that member countries will be willing to renegotiate the already signed deal.

Obama has promoted the TPP as a once-in-a-generation opportunity for trade expansion but he has lost support from many Democrats, including presidential candidates Sen. Bernie Sanders (I-Vt.) and Hillary Clinton.

The Obama administration has said that the agreement includes the strongest worker protections in any trade agreement as well as commitments from member countries to avoid currency manipulation.

“We’re disappointed but not surprised given Congressman Levin’s votes against trade promotion authority and the trade enforcement bill,” said assistant U.S. Trade Representative for Public Affairs Matt McAlvanah. “In TPP, we’ve made historic progress on issues important to House Democrats and look forward to continuing to work on a bipartisan basis to move legislation forward.”