As NAFTA talks intensify in Washington, Canada’s dairy farmers implored Prime Minister Justin Trudeau not to trade access to the country’s protected milk market for a deal with the U.S.

Pierre Lampron, president of the Dairy Farmers of Canada, says the industry has already lost $250 million in annual business from concessions in past trade agreements and won’t accept further losses.

“The whole work of our lives seems to have been reduced to a bargaining chip,” Lampron told reporters Wednesday in Ottawa. “The dairy sector can’t once again be negatively impacted by another trade deal. Enough is enough.”

Lampron and his colleague David Wiens, chairman of the Dairy Farmers of Manitoba, say producers will hold Trudeau to account for his pledge to defend a system known as supply management, a threat that may have added resonance given the approach of federal elections in about a year’s time. Canada’s market is too small to cope with U.S. overproduction, and even Class 7 milk targeted by U.S. President Donald Trump for having high restrictions is worth protecting.

“We hold our prime minister to his promise and his statement that he will defend supply management and dairy in the context of the Nafta negotiations,” Wiens said at the same Ottawa event. “We have articulated to him very clearly that support for supply management, support for dairy, means that there is no access given.”

Trump has regularly pressed for dairy concessions as essential for a NAFTA deal.