A key labor leader has warned House Democrats not to expedite approval of a new North American trade deal, saying that the agreement remains far from complete and that a vote in coming weeks would be a “colossal mistake.”

“If there was a vote before Thanksgiving, the agreement would be defeated,” AFL-CIO President Richard Trumka told The Washington Post this week in an interview. Support from the 12.5 million-strong AFL-CIO would be critical in persuading many House Democrats to back the new trade deal, giving Trumka enormous sway in negotiations.

Trumka’s comments come as the U.S. Chamber of Commerce pushes for a vote by Thanksgiving. Republican lawmakers and Trump administration officials are also trying to ramp up pressure on House Democrats to get the deal done, although there are conflicting signals about how the impeachment inquiry of President Trump will affect the process.

House Democrats have spent months negotiating with the Trump administration on an update to the 25-year-old North American Free Trade Agreement. Trump brokered a deal to revise the trade pact with Canada and Mexico last year, but Congress must still approve it.

House Speaker Nancy Pelosi (D-Calif.) has avoided laying out a timetable, saying that the deal would be brought to the House floor when it’s ready. But she has also sounded notes of optimism and urgency, telling reporters last week: “We are on a path to yes.”

House Democrats’ new impeachment inquiry of Trump has clouded prospects for the U.S.-Mexico-Canada-Agreement, as the new trade pact is known. Some Democrats have voiced concerns about Trump’s willingness to strike a deal with them while an impeachment inquiry is underway, and Trump has suggested that Democrats are the ones incapable of simultaneously legislating and impeaching.

“The Do Nothing Democrats don’t have time to get it done!” the president tweeted last week about the trade deal.

Behind the scenes, though, negotiations have continued between House Democrats, led by Ways and Means Chairman Richard E. Neal (D-Mass.), and administration officials, led by U.S. Trade Representative Robert E. Lighthizer.

Neal and a group of lawmakers traveled to Mexico this week to meet with President Andrés Manuel López Obrador and other officials. They discussed one of the major sticking points in negotiations: Mexico’s ability to implement and enforce fair labor standards in a way that will protect workers in that country and in the United States. This issue has been a major concern for labor groups.

Higher wages and standards in Mexico would lessen incentives for U.S. companies to relocate manufacturing to that country. Many U.S. workers and labor leaders contend that the original NAFTA led many U.S. companies to relocate manufacturing operations to Mexico and decimated blue-collar jobs. A key goal for Democrats negotiating the new deal is to make sure that does not happen again.

But Trumka said that Mexico faces enormous challenges in implementing the necessary changes, including the need for a major new budgetary commitment to support enforcement mechanisms that would ensure labor reforms. Thus far, Trumka said, it’s far from clear that those changes will be made.

“If they can’t enforce their own laws, we have a real problem," he said. “No agreement will be able to work.”

Rep. Bill Pascrell Jr. (D-N.J.), a skeptic of the deal, was among those who traveled to Mexico with Neal this week. Pascrell said he was impressed by López Obrador’s understanding of the challenges and his commitment to making the changes needed.

“He really is a breath of fresh air,” Pascrell said in an interview. “But the only thing is, this is so deep and entrenched in past behavior that I’m questioning whether we can really put a document together that would protect not only the laborers and workers of Mexico, but also the workers of the United States of America.”

Rewriting NAFTA was one of Trump’s major campaign promises in 2016. It’s also the top legislative item on Congress’s thin to-do list ahead of the 2020 election, apart from spending bills needed to keep the government open. Amid signs of a weakening economy that some analysts attribute in part to Trump’s trade wars with China and other nations, signing a new trade pact with Canada and Mexico would be a major win for the president as he seeks reelection. Privately, some House Democrats express anxiety about giving Trump that win — and also about the possibility of Trump blaming them if no deal is reached.

But many argue that negotiating a new trade deal that’s good for American workers would be a win for Democrats, too, especially in the manufacturing and farming states and districts that will be critical in the election. That may be especially true for House Democrats from closely divided districts who want to be able to argue that they can produce bipartisan accomplishments despite the rancor of impeachment.

“I think it’s just good politics when you achieve results, and I think everyone knows this wouldn’t happen without the cooperation and the work of Nancy Pelosi and her team,” said former senator Heidi Heitkamp (D-N.D.), who co-chairs the advocacy group Trade Works for America. “You can say well it would be a big win for the president. If it’s a big win for the president, it’s a big win for the House majority as well.”

But the process could bog down if Democrats don’t win the backing of labor groups, something that continues to elude them as they feel pressure from Republicans and business groups to resolve differences.

“If we can get these things fixed, we can get to yes," Trumka said. “If we can’t get them fixed, we can’t get to yes."