Sanders and Warren, who polls show are top contenders for the Democratic nomination, have long criticized Washington trade policies they say have hurt workers and the environment.

They are also fiercely critical of Trump, making it difficult to see how they could back a deal he has already touted as a major achievement.

“Donald Trump will be spending the next 11 months bragging about the trade agreement he ‘alone’ passed, despite the political capital Democrats sunk into making sure NAFTA 2.0 was slightly better than the deal it’s replacing,” said Yvette Simpson, the CEO of Democracy for America, a liberal advocacy group.