Teamsters President James P. Hoffa applauded the Canadian government Thursday for using the North American Free Trade Agreement renegotiations to pressure the U.S. into banning state right-to-work laws.

Hoffa urged Canada's negotiators to "hold their ground" against the U.S.' own negotiators. Right-to-work laws prohibit workers from being forced to join or otherwise support a union as a condition of employment. Labor leaders dislike the laws because they are associated with membership losses and depleted treasuries.

"Teamsters in the U.S. are mobilized against the spread of so-called ‘right-to-work' laws in the states because they depress wages by undercutting union power," Hoffa said Thursday at a Washington press conference held by U.S. and Canadian labor leaders. "I applaud the Canadians for making this a trade issue. We agree that these laws incentivize employers to relocate from Canadian provinces that don't allow 'free-riders.' I urge the Canadian negotiators to hold their ground on their progressive labor text and for the U.S. negotiators to take this issue seriously."

Right-to-work advocates scorned the Hoffa's comments. "It's insulting to the hard-working men and women of America that union bosses' 'solution' to practically every issue is to strip more workers of their freedom to decide for themselves whether or not to support a union with their hard-earned money. Right-to-work simply gives workers freedom of choice, and if NAFTA is going to deal with right-to-work at all it should be to expand that freedom to Canada and Mexico, not attack a policy supported by eight in 10 Americans," said Patrick Semmens, spokesman for National Right To Work.

The fourth round of talks to renegotiate NAFTA began Wednesday in Arlington, Va., and will continue through next week. Canadian negotiators, pressed by their labor unions, have been using the talks to press the U.S. to pass a federal law banning right-to-work. The U.S. is reportedly resisting Canada's request. President Trump said during the 2016 presidential campaign that he supports right-to-work.

State right-to-work laws specifically prohibit union-management contracts that require all workers join a union or pay one a regular fee or else lose their job. The provisions, dubbed "security clauses" by unions, are common in non-right-to-work states. Unions argue they are owed the money to pay for collective bargaining expenses that benefit all workers. Business groups and Republicans back the laws, arguing they give states an edge in attracting business and that joining a union should be a decision left up to individual workers.

A total of 27 states have the laws. Five states have adopted them since 2012, including Michigan and Wisconsin, both of which border Canada. Another state, Missouri, passed one but it is on hold pending the outcome of a voter referendum next year. The surge in popularity of the laws has left labor groups scrambling to find a way to prevent them from spreading further.