An emerging trade irritant between Canada and the United States that had been quietly simmering for months has now bubbled into the open.

The Canadian government sent a letter to nearly a dozen senior U.S. officials Friday expressing dismay over an idea being considered in a key American budget bill.

As reported last week by CBC News, Canadian officials have been concerned about a Buy American-type proposal they fear might disrupt the auto sector.

Now Ottawa has put those views in writing to the congressional leadership from both parties, other key members of Congress and two cabinet-level officials.

Minister of International