A group of liberal lawmakers led by Sens. Bernie Sanders and Elizabeth Warren wrote President Trump Friday urging him to continue to push for reforms to the North American Free Trade Agreement.

The requests from the Vermont independent and Massachusetts Democrat included major changes to the 1993 U.S.-Canada-Mexico trade deal's investor-state dispute settlement system and rules for country of origin labeling, areas where their goals overlap with the president's although they did not acknowledge that in the letter.

"We urge you to renegotiate NAFTA to deliver a deal we can support," the lawmakers said. "However, unless you are able to succeed in negotiating a new deal that meets the criteria enumerated below, companies will continue to move U.S. jobs to Mexico to pay workers poverty wages and dump toxins and then import those products back for sale here in the United States."

In addition to Sanders and Warren, the letter was signed by Democratic Sens. Jeff Merkley of Oregon, Edward Markey of Massachusetts, and Kirsten Gillibrand of New York.

The letter calls for, among other changes to NAFTA, the elimination of the deal's investor-state dispute settlement policy, saying it reinforces a system that "makes it easier and cheaper to outsource jobs." U.S. Trade Representative Robert Lighthizer has pushed for allowing NAFTA members to opt out of the system, which the letter does not acknowledge.

The senators also call for "strengthened rules of origin ... in order to incentivize production in North America in general and the United States in particular." The administration has asked for raising the standard for cars and trucks to be declared "made in America" from 62.5 percent of the components coming from North America to 85 percent and to require that at least half of the components come from the U.S. The letter does not acknowledge that, either.

Spokespeople for Sanders and Warren could not be reached for comment.

Canada and Mexico have resisted both U.S. efforts, and the talks have been strained, prompting Trump and other administration officials to reiterate earlier threats to withdraw from the deal altogether if Canada and Mexico do not make concessions. The talks are expected to continue through the summer.