Sen. Bernie Sanders (I-Vt.) delivers a speech during J Street's 2017 National Conference at the Washington Convention Center on Feb. 27, 2017, in Washington. The theme was “Defending Our Values, Fighting For Our Future.” (Mark Wilson/Getty Images)

Sen. Bernie Sanders (I-Vt.) and several progressive senators are laying out their demands for changing the North American Free Trade Agreement, hoping the Trump administration will side with them as it renegotiates the pact.

The demands — detailed Friday in a letter to the White House from Sanders, Elizabeth Warren (D-Mass.), Kirsten Gillibrand (D-N.Y.) and others — in some cases match changes President Trump's team is pushing in talks with Mexico and Canada.

Trump and the progressives, however, split sharply on labor standards, environmental protections and other key aspects of the trade pact, making it unlikely that progressive Democrats would endorse the administration's approach.

“We urge you to renegotiate NAFTA to deliver a deal that we can support,” says the letter, which was backed by labor groups like the AFL-CIO and environmental groups like the Sierra Club, as well as Sens. Jeff Merkley (D-Ore.), Mazie Hirono (D-Hawaii), and Edward J. Markey (D-Mass.). “There is broad public support nationwide and across partisan divides to replace the current rigged U.S. trade agreement model epitomized by NAFTA.”

The letter’s demands include stripping protections for investors and other incentives that critics say encourage outsourcing — matching positions Trump’s team is already bringing to the table.

“The surprising and exciting thing is how much overlap there is between the administration’s proposal and progressive demands about removing NAFTA’s job outsourcing incentives,” said Lori Wallach, of the left-leaning nonprofit watchdog Public Citizen. “The problematic part is that, so far, the necessary environmental and labor standard improvements have not been proposed, and some rollbacks of consumer protections are on the agenda.”

Another area of overlap between the Trump team’s demands and those of progressives is the curtailment of the panels used to resolve trade disagreements between nations and corporations, derided by critics as “secret tribunals.” These tribunals are also targeted in the senators' letter, and U.S. Trade Representative Robert E. Lighthizer has moved to eradicate certain aspects of that process.

“I’d be surprised if they go as far as progressives would like them to do, but we’re encouraged by what they’re trying,” said Robert Scott, an economist at the Economic Policy Institute, a left-leaning think tank.

The two sides also largely agree on rolling back NAFTA rules they say allow governments to waive clauses in government contracts mandating they purchase products made in America. Populists on the left have long called for changes to this position, and Lighthizer has also identified it as one of America's top priorities in the talks. (It is unclear whether  Mexico and Canada will be willing to sign off on the requested changes.)

“It’s not quite as far as we’d like, which is it to take it out, but it’s definitely barking up the right tree,” said Wallach, of Public Citizen. She also praised Lighthizer for pushing for a new provision that would force all three countries to review and re-ratify NAFTA every five years, another position called for in the letter spearheaded by Sanders.

Despite the overlap, the gulf between the president and the senators remains wide. Sanders, Warren, and Gillibrand are all rumored presidential candidates for 2020, and their letter suggests the avenues through which they may attack Trump over trade in the event he either fails to renegotiate NAFTA, or does so in a way that falls short of their demands.

The Trump administration has not publicly demanded the inclusion of stricter worker and environmental standards in the deal, and the senators are calling on the administration to enshrine in NAFTA the conventions of the International Labor Organization, which include the right of workers to form labor unions, rules against discrimination and the abolition of forced labor.

“That’s the very bad news: There still hasn’t been a proposal from the U.S. to improve the labor standards in NAFTA,” Wallach said.

The senators' letter also specifies the administration push to align NAFTA with the international Paris climate agreement, which would impose limitations on carbon emissions. Trump announced last year that America will pull out of the accord and has ridiculed climate change as a “hoax” in the face of overwhelming academic consensus.

Some academics argue the demands outlined by the progressives are impossible for negotiators to meet without scrapping the deal altogether, and argue that Mexico and Canada already have strong environmental and labor protections. Even if negotiators agreed to enforce stricter labor standards, they say, a new deal would be unlikely to bring jobs back to the United States because wages in Mexico would still be far lower.

“In many instances, it’s not clear what the critics of NAFTA wanted other than the ending of NAFTA — so it’s hard to rally the sides to a positive agenda for, ‘Here is what new NAFTA 2.0 should look like,” said Anupam Chander, a professor at University of California at Davis who studies NAFTA and trade deals. “It’s hard for the Trump administration to actually placate the Sanders folks.”

Others say there is room for NAFTA to be aligned with more progressive environmental and labor standards without eliminating it altogether.

“The world is a messy place, and there’s not going to be a grand solution everything,” said Jonathan Aronson, a professor who focuses on trade issues at the University of Southern California. “But can you improve things on the labor side or on the environment? Absolutely.”