A group of 40 House Republicans have called on President Donald Trump to kill LGBT protections found in the trade deal between Canada, Mexico and the United States.

According to Politico, the NAFTA update includes a provision that encourages countries to adopt policies prohibiting discrimination based on sexual orientation and gender identity in the workplace. The provision was included at the request of Canada.

In a letter to Trump sent Friday, the conservative lawmakers threatened to pull their support for the deal if the language is not removed.

“A trade agreement is no place for the adoption of social policy,” the lawmakers wrote.

“It is especially inappropriate and insulting to our sovereignty to needlessly submit to social policies which the United States Congress has so far explicitly refused to accept,” they added, a reference to the lack of such protections at the federal level.

Representatives Steve King of Iowa, Vicky Hartzler of Missouri and Louie Gohmert of Texas are among the 40 Republicans who signed the letter. King, Hartzler and Gohmert scored zero on the Human Rights Campaign's (HRC) latest Congressional Scorecard, a measure of a lawmaker's support for LGBT rights.

(Related: Steve King: Gay marriage ruling means “you can marry my lawnmower.”)

Colorado Congressman Doug Lamborn, who also signed the letter, told Politico that the LGBT provision could kill the entire agreement, which requires approval from Congress.

“At this point I'm a 'no' vote and I would encourage others to be a no vote unless something is done,” Lamborn said. “And things could be done within the agreement.”