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By Eric M. Johnson

LE BOURGET, France, June 18 (Reuters) - Korean Air has provisionally ordered 20 Boeing Co 787 Dreamliner passenger jets and agreed to lease another 10, the companies said on Tuesday, giving the world's largest planemaker a needed boost after a subdued start to the Paris Airshow.

The deal includes a commitment to purchase 10 new 787-10s and 10 additional 787-9 airplanes with the total agreement valued at $6.3 billion at current list prices, the companies said.

Korean Air, one of the largest transpacific carriers in Asia, said it would add the larger 787-10 to its longer haul fleet of 787-9 and 777 airplanes.

The order gives Boeing a lift as it grapples with the financial fallout over the grounding of its fastest-selling 737 MAX model in the wake of deadly crashes. (Reporting by Eric M. Johnson; Editing by Mark Potter)