The White House triggered a process Thursday that would allow President Trump to submit his new trade deal with Canada and Mexico to Congress after 30 days, three people briefed on the planning said, a direct challenge to House Speaker Nancy Pelosi (D-Calif.) who had warned against such a step.

The decision to send the draft “Statement of Administrative Action” to Congress marks a milestone in Trump’s push to overhaul the 1994 North American Free Trade Agreement, but it heightens tensions with Democrats who have said they need more time to review the deal and work for changes.

Pelosi directly cautioned U.S. Trade Representative Robert E. Lighthizer not to send the draft report until Democrats have spent more time working with the White House on the plan. And on Thursday, she attacked the White House’s decision to move ahead.

“It indicates a lack of knowledge on the part of the Administration on the policy and process to pass a trade agreement,” she said in a statement.

By filing the report with Congress, the White House signaled that it does not plan to allow Democrats to delay the process and will push for a vote soon. (Even as the White House filed the report, Trump announced late Thursday a plan to impose tariffs on Mexico if it fails to stem the flow of undocumented immigrants into the United States. Such a move would probably undermine efforts to complete the new trade deal.)

A number of White House officials had urged their colleagues in the West Wing to heed Pelosi’s advice and slow the process down in a way that builds support among Democrats, a senior administration official said. But other White House officials felt Pelosi needed to be pressured for her to stop dragging the process out, and Trump wants a revised NAFTA deal to be one of the top accomplishments of his first term.

“You have to send the language up and pressure her,” said the senior administration official, who spoke on the condition of anonymity to discuss the internal deliberations. “This is absolutely ridiculous.”

Sending the draft to Congress is a necessary step before lawmakers can formally vote on the agreement. The White House cannot send the formal agreement to Congress until 30 days after the draft is sent to Congress, which means Thursday’s step will launch that timeline in earnest. Still, the administration could wait beyond 30 days to submit the final text of the trade deal.

Pelosi and other Democrats have said they want assurances that the new trade deal will include enforceable rules related to environmental and labor policy, among other things.

“We all agree that we must replace NAFTA, but without real enforcement mechanisms we would be locking American workers into another bad deal,” Pelosi said Thursday. “A new trade agreement without enforcement is not progress for the American worker, just a press release for the President.”

In a letter to Pelosi on Thursday, Lighthizer attempted to make clear that he still planned to work with lawmakers on these issues and that the draft report did not preclude him from addressing their concerns. Submitting the draft “does not limit our ability to find solutions to address concerns Members have raised about enforcement of the labor and environmental provisions of the Agreement and pharmaceutical pricing,” Lighthizer wrote.

The new trade deal, the United States-Mexico-Canada Agreement, aims to encourage more automotive and other manufacturing in North America by making it harder to avoid import penalties on products made in China and elsewhere. The rules would require higher wages for many workers, open up Canadian dairy markets for U.S. farmers and strengthen intellectual property protection. It would also help a range of other industries, including pharmaceutical companies.

Trump brokered many details of the agreement last year during tense negotiations with Canada and Mexico, but the changes cannot be finalized until the House and the Senate vote to approve the deal, something White House officials have said they want to happen this year.

Vice President Pence was in Canada on Thursday meeting with Canadian Prime Minister Justin Trudeau to discuss completing the agreement.