SINGAPORE (Reuters) - Singapore Airlines Ltd SIAL.SI said on Friday it will finalize an order for 39 Boeing Co BA.N aircraft worth $13.8 billion at list prices when Singaporean Prime Minister Lee Hsien Loong visits Washington D.C. next week.

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The airline said in February it would order 20 777-9 and 19 787-10 widebodies as part of plans to modernize its fleet over the next decade, but the deal is yet to be finalised and placed in Boeing’s order book as a Singapore Airlines order.

The deal was viewed as a major blow to Airbus SE AIR.PA as it battles against Boeing in the widebody market. Airbus has lagged Boeing in net orders in the first nine months of the year, with 271 at the end of September versus 498 for its U.S. rival.

Lee told CNBC television on Thursday that he hoped an agreement would be signed with Boeing to buy more aircraft for Singapore Airlines during his U.S. visit from Oct. 22 to 26.

More details about the order would be revealed after the signing ceremony in Washington, a Singapore Airlines spokesman said.

The airline in February said it had also acquired options to order six more aircraft of each type.

Boeing in June booked orders for 20 777Xs and 19 787-10 aircraft for an unidentified customer or customers, making it possible the Singapore Airlines aircraft are already counted in this year’s net orders. Boeing declined to comment.

Singapore Airlines is investing in modern, fuel efficient aircraft while at the same time undertaking a strategic review designed to help cut costs amid growing competition from Chinese and Middle Eastern rivals.

While the Boeing order is worth $13.8 billion at list prices, airlines typically get discounts on jet orders. Jefferies in February estimated the deal’s value at closer to $6.5 billion, or about a tenth of the U.S. plane maker’s annual volume.

Singapore Airlines is the launch customer for the 787-10, a stretch version of the Dreamliner, having made 30 firm orders in addition to the 19 announced in February. Boeing completed final assembly of the airline’s first 787-10 earlier this month ahead of delivery in the first half of 2018.