MONTREAL >> The U.S. International Trade Commission today struck down a Commerce Department recommendation that the United States place steep duties on imported Canadian jets, a surprise decision in a trade dispute that has stoked tensions between normally close allies.

The ruling ends a case bought by Boeing, which accused the Canadian jet maker Bombardier of subsidizing its products and selling them at unfairly low prices in the United States in violation of U.S. trade rules in a way that threatened sales of Boeing’s Max 7.

The Commerce Department had decided that duties of nearly 300 percent should be placed on Bombardier’s new CSeries aircraft. But the trade commission, a quasi-judicial body of trade experts, disagreed. It did not release any information on the factors determining its decision.

In a statement, Bombardier described the decision as “a victory for innovation, competition, and the rule of law.” It added that it looked forward to delivering the CSeries plane to the U.S. market.

Boeing, in its own statement, said it was disappointed in the decision and continued to experience “the effects of those unfair business practices in the market every day.”