UPDATE 1-U.S. trade body continues probe into dumping claims against Bombardier jets

Bombardier jets@ (Adds background and details about probe and dispute between Boeing and Bombardier, paragraphs 2-10)

WASHINGTON, June 9 (Reuters) - The U.S. International Trade Commission on Friday voted to continue an investigation into Boeing Co's complaint that Canada's Bombardier Inc dumped its CSeries jet below cost in the U.S. market while benefiting from unfair subsidies.

The vote, which was largely expected, is the first step in a case that could lead the United States to impose steep duties on Bombardier's newest 110- to 130-seat jets.

In voting 5-0 to continue the probe, ITC commissioners found there was sufficient evidence that Boeing may have suffered an injury. The Commerce Department must now determine any preliminary anti-subsidy duties by around July 22, with a deadline for preliminary anti-dumping duties at around Oct. 3.

The case has fueled trade tensions between the United States and its northern neighbor, with Canada calling on Boeing to abandon the anti-dumping challenge, and threatening to scrap plans to buy the company's fighter jets.

Boeing has argued that the CSeries program would not exist without hundreds of millions of dollars in launch aid from the governments of Canada, Quebec and Britain, or a $2.5 billion equity infusion from Quebec and its largest pension fund in 2015. It warned that Bombardier's actions could upset the wider market and erode future sales of Boeing's best-selling 737.

Boeing wants the U.S. government to investigate the 2016 sale of 75 CSeries aircraft to Delta Air Lines for what the American planemaker calls the "absurdly low" sum of $19.6 million each, despite the jet costing $33 million to build.

Bombardier, which described Boeing's $19.6 million figure as "absurd," has countered that the 110-seat CS100 plane it sold to Delta does not compete with Boeing's smallest 737 model, the 130-seat 737 MAX 7.

Bombardier recently dismissed industry suggestions that the row could slow efforts to accelerate sales of its CSeries jet.

If the U.S. Commerce Department investigation finds that duties on the Bombardier aircraft are warranted, these would be aimed at offsetting any below-cost pricing or subsidies deemed unfair. The International Trade Commission would conduct its own probe with testimony from both sides and vote on whether to confirm or reject any duties. (Additional reporting by Allison Lampert in Montreal and Eric Walsh in Washington; Editing by Jeffrey Benkoe)