BARCELONA, Spain (Reuters) - Airbus appeared close on Monday to breaking into one of rival Boeing's strategic markets with a multi-billion-dollar deal to sell jets to Japan, two sources familiar with the matter said. The deal is expected to involve the sale of A350 aircraft to Japan Airlines Co Ltd (9201.T) and follows an intense battle between the planemakers as Japan's two top carriers seek dozens of new long-haul jets over the next decade, the sources said. They gave no details on the number of planes expected to be sold. In France, Airbus said it would hold a telephone briefing at 0430 GMT on Monday, but declined to give further details. There was no immediate indication whether the briefing concerned an aircraft order. In Tokyo, JAL was not immediately available for comment. Industry sources said in August that U.S. planemaker Boeing (BA.N) had edged ahead in a see-saw contest with its European rival as it defends a market share of around 80 percent in Japan, where it has strong ties to suppliers. But both sides have been seen as striving to win coveted endorsements for their latest long-distance jets from JAL and its domestic rival All Nippon Airways (9202.T). Industry sources have said both airlines are looking for around 25 aircraft. A deal for that number of A350s would be worth some $7-8 billion at list prices, depending on the type. Boeing is looking for Japanese support for a proposed revamp of its best-selling 777 long-haul jet, while Airbus is pushing a larger version of its upcoming A350 aircraft. Airbus sales chief John Leahy told Reuters last month he had "not given up" efforts to land new aircraft orders in Japan, where Boeing has long been the dominant supplier and flag carrier JAL has yet to order Airbus aircraft. ANA (9202.T) said last month it would consider the risk of delivery delays when choosing between the A350, whose base model enters service in 2014, and Boeing's yet-to-be-launched "777X." (Reporting by Tim Hepher in Barcelona and Tim Kelly in Tokyo. Editing by Dean Yates)