House Speaker Nancy Pelosi suggested Tuesday that President Trump must reopen talks with Canada and Mexico to tighten enforcement provisions in a proposed North American trade deal, casting renewed doubt on prospects for congressional ratification of the accord.

“No enforcement, no treaty,” she said, offering some of her most pointed remarks to date on the fate of a measure that the administration has labeled its top trade priority.

Pelosi’s comments, at a Politico event in Washington, came one day after AFL-CIO President Richard Trumka told reporters that negotiators should return to the bargaining table to strengthen the enforcement provisions.

“It does suggest that the speaker is willing to take this beyond 2019,” said Dan Ujczo, a trade attorney with Dickinson Wright. “That’s going to take some time to negotiate with Mexico and Canada.”

Any delay could complicate the deal’s path to approval as attention turns to the 2020 presidential campaign.

The administration, which negotiated the new trade accord in 13 months of breakneck diplomacy, opposes reopening the negotiations. Robert E. Lighthizer, the president’s chief trade representative, says the U.S. instead could use the threat of unilateral tariffs under Section 301 of the 1974 Trade Act to enforce the deal.

Lighthizer has sought organized labor’s support for the agreement, so far without success. Unions blame the original 1994 North American Free Trade Agreement (NAFTA) for the loss of millions of factory jobs, as corporations relocated production to Mexico to take advantage of cheaper wages.

Pelosi, who voted for NAFTA and said she felt “burned” by the experience, is demanding changes to the new agreement to prevent a repeat.

Democrats also want tougher language on labor and environmental protections, which could be addressed in legislation. But enforcement terms must be written directly into the agreement with U.S. trading partners, she said.

“Enforcement has to be in the treaty,” she said at the Politico event.

The speaker’s stance could increase pressure on the White House to woo Democrats with an offer of backing for infrastructure spending or a pathway to citizenship for undocumented immigrants known as the “dreamers,” Ujczo said.

Addressing Pelosi’s concerns won’t necessarily delay ratification, according to one business lobbyist who asked for anonymity to speak candidly. Most trade agreements are ratified only after some last-minute issues are resolved by reopening talks or adding a side letter that carries equal force, the executive added.

“At the end of the day, any talk about reopening or doing a side letter is kind of irrelevant,” he said. “If there’s a will, they can get around that.”

The U.S. Trade Representative’s Office did not reply to a request for comment.

Pelosi also said that she would not bring up the U.S.-Mexico-Canada Agreement for a floor vote until Mexico approves promised labor reforms.

To comply with USMCA, Mexico needs to pass legislation strengthening workers’ collective bargaining rights, providing free and fair union elections, and establishing independent labor courts.

The agreement called for Mexico to pass the required legislation by January 1, a deadline that came and went. Mexican officials, however, insist that populist President Andrés Manuel López Obrador is committed to labor reforms. In February, Mexican diplomats visiting Washington predicted passage by the end of April.

“Entry into force of this Agreement may be delayed until such legislation becomes effective,” the text warns.

Meanwhile, a major business group said the administration is inching closer to a trade deal with China.

Talks are scheduled to resume Wednesday in Washington between Lighthizer and Chinese Vice Premier Liu He with officials hoping to wrap up an agreement this week.

“We’re optimistic that the two governments are going to get a deal,” said Myron Brilliant, executive vice president of the U.S. Chamber of Commerce. “We have been encouraged at the tone in the negotiations.”

Some stumbling blocks remain. China wants the U.S. to drop all of the tariffs it imposed on more than $250 billion in Chinese goods last year. Lighthizer, meanwhile, wants China to accept that the U.S. will enforce the deal with unilateral tariffs and that it cannot retaliate — something Beijing is resisting.

Brilliant, who recently returned from speaking with Chinese officials in Beijing, said roughly 90 percent of the deal has been ironed out. But the remaining work represents “the toughest and trickiest decisions,” he said.

“We’re getting into the end game stage,” he said.