U.K. Prime Minister Theresa May asked U.S. President Donald Trump to intervene in a court dispute between Boeing Co. and Canada’s Bombardier Inc. over state aid, her office said.

The request, made in a call with the president on Sept. 5, came as her government seeks to protect jobs at a Bombardier plant in Belfast, Northern Ireland. May’s government relies on votes from Northern Ireland’s Democratic Unionist Party to pass legislation through the House of Commons.

May is expected to discuss Boeing and other issues with Canadian Prime Minister Justin Trudeau during a visit to Ottawa on Sept. 18, a Canadian government official said, speaking on condition they not be identified since a formal announcement has not been made. May raised the case with Trump after the intervention of DUP leader Arlene Foster, the Times of London newspaper reported, without saying where it got the information.

“Our priority is to encourage Boeing to drop its case and seek a negotiated settlement with Bombardier,” the U.K. Department for Business said in an emailed statement. “This is a commercial matter but the U.K. government is working tirelessly to safeguard Bombardier’s operations and its highly skilled workers in Belfast.”

Boeing is pressing the U.S. International Trade Commission to impose tariffs against its Canadian competitor over sales of its C Series jets at “absurdly low prices” while receiving unfair government support, including a 113 million-pound ($149 million) loan from the British government. The commission ruled in June that Boeing may have been harmed by sales of C Series aircraft at less than fair value.

Boeing said in a statement that it is seeking to restore “a level playing field” in the U.S. single-aisle airplane market.

“Boeing had to take action as subsidized competition has hurt us now and will continue to hurt us for years to come, and we could not stand by given this clear case of illegal dumping,” the company said.

“This is the normal course of action for addressing instances where a competitor is selling into the U.S. market below cost, and we will let the process play out,” it added. “We believe that global trade only works if everyone plays by the same rules of the road, and that’s a principle that ultimately creates the greatest value for Canada, the United Kingdom, the United States and our aerospace industry.”

Bombardier has criticized Boeing’s complaint, calling it an “unfounded assault” on airlines.

“We are very confident the U.K. government understands what is at stake and will take the actions necessary to respond to this direct attack on its aerospace industry,” spokesman Bryan Tucker said in a written statement today.

Alongside May’s intervention, Business Secretary Greg Clark traveled to Chicago to meet with Boeing executives to try to find a solution to the dispute and safeguard about 4,500 jobs in Bombardier’s Northern Ireland unit, his office said.

David MacNaughton, Canada’s Ambassador to Washington, told reporters today that Boeing had walked away from talks with his government over the issue and that he has now raised it with U.S. Commerce Secretary Wilbur Ross.

“For whatever reason they decided they weren’t going to continue to have discussions,” MacNaughton said, adding Boeing’s complaint stems from the sale of planes to Delta Air Lines Inc., a purchase that he said Boeing was not even competing for.

Bombardier’s C Series plane “does not compete against any Boeing aircraft on the Delta sale,” MacNaughton said, adding: “What we’re trying to understand is what they’re objecting to.”