Donald Trump said Monday that if the House of Representatives doesn't pass last year's trade deal known as the United States-Mexico-Canada Agreement (USMCA), it will all be Nancy Pelosi's fault.

'It's sitting on Nancy Pelosi's desk. She's incapable of moving it, it looks like. She can't,' Trump told reporters in the Oval Office. 'Everybody knows it's a great deal. She knows it's a great deal, she said it. She keeps saying she wants to get it done but we're talking about many months sitting on her desk, no votes.'

The president said most Democrats 'and I guess all of the Republicans' would vote to green-light the deal.

'All she has to do is say we are putting it up for a vote, like immediately,' Trump complained, warning that 'you're going to have Mexico and Canada pull it pretty soon. And if they do, it's her fault, not mine. We gave you a great deal.'

'I wouldn't blame them at all and that's okay. We'll just blame Nancy,' Trump announced.

'House Democrats have insisted that hard-working Americans need more from the USMCA than just the same broken NAFTA with better language but no real enforcement,' Pelosi said in a statement in response.

'We are within range of a substantially improved agreement for America’s workers. Now, we need to see our progress in writing from the Trade Representative for final review,' she added.

Mexico's government on Monday ramped up pressure on Pelosi to approve the USMCA, rejecting demands for greater oversight of its labor market. President Andres Manuel Lopez Obrador said he would send her a second letter this week to press for congressional ratification.

Donald Trump said Monday that if the House of Representatives doesn't pass the USMCA trade deal, it will all be Nancy Pelosi's fault

U.S., Canadian and Mexican leaders have all signed off on the trade agreement, but American law requires Congress to ratify such treaties; Pelosi is the bottleneck, even as Mexico has ratified it

'I'm sure that Mrs. Pelosi and the lawmakers of the Democratic Party are going to help us,' Lopez Obrador told a regular news conference, saying he believed the U.S. Congress would approve the deal before the end of 2019.

Trump said Pelosi has been hesitant because labor unioins including the AFL-CIO 'are asking her to hold it for a while because it makes Trump look bad.'

Lopez Obrador said his understanding was that both U.S. President Donald Trump, who had pushed for the deal, and Republican lawmakers, agreed the USMCA should be ratified soon.

Still, standing alongside Lopez Obrador, Jesus Seade, deputy foreign minister for North America and the Mexican official in charge of USMCA negotiations, said he was 'pessimistic' the accord would be approved by U.S. lawmakers before 2020.

'Far from reaching a deal, in the last two weeks, statements from certain labor sectors have re-emerged, floating ideas that would be totally unacceptable to Mexico,' Seade said.

Mexican President Andres Manuel Lopez Obrador said Monday that 'I'm sure Mrs. Pelosi and the lawmakers of the Democratic Party are going to help us

Mexico, which ratified the USMCA earlier this year, is eager for the agreement to be approved because the country's exports and foreign direct investment are heavily dependent on having unfettered access to the U.S. marketplace.

U.S. lawmakers, notably Democrats, have held up the process over concerns that lower-cost Mexico will continue to be able to attract investment at the expense of U.S. workers.

Lopez Obrador's left-leaning government has pledged to improve workers' pay, and earlier this year pushed through a labor bill that will strengthen the rights of trade unions.

The president, Seade and Foreign Minister Marcelo Ebrard all underlined that Mexico had fulfilled its commitments under the USMCA framework as they urged Congress to pass the deal.

However, Democrats have sought assurances from Mexico that measures to strengthen workers' rights will be enforced, causing friction with the Lopez Obrador administration.

Among the sticking points have been U.S. attempts to establish dispute panels for labor, Seade said. Mexico's position is that panels should be allowed across the board, not for specific areas, he noted.

Enforcement remained a bone of contention, Seade said, noting that there were those on the U.S. side seeking to impose 'more intrusive' mechanisms to bind Mexico.

'We told them we won't accept that,' he said.

The USMCA was agreed after a lengthy negotiation to replace the 1994 North American Free Trade Agreement (NAFTA).