By Nicholas P. Brown

Oct 31 (Reuters) - Boeing Co delivered its first KC-46A aircraft to Japan, the company said on Sunday, the first delivery of the aerial refueling jet to a customer outside the United States, as growing tensions with China spur Japan to ramp up defense spending. The Japan Air Self-Defense Force (JASDF) took delivery of the jet under a contract first signed in 2017. Boeing in a statement called the delivery a "significant milestone" for U.S.-Japan cooperation in the Indo-Pacific region.

The U.S. Air Force and JASDF initially awarded a contract for one KC-46A, but have since exercised options for three more of the jets. Boeing touts the aircraft as its most state-of-the-art refueling tanker, equipped with advanced sensors and capable of carrying cargo and passengers as it refuels other planes.

Still, the KC-46 line used by the U.S. Air Force has run into performance snags https://www.reuters.com/business/aerospace-defense/air-force-exploring-options-next-batch-midair-refueling-tankers-2021-06-16, including defects with an on-board video system.

Sunday's delivery comes at a tense time for Japan, as it looks to counter China's military assertiveness in Asia.

The country's ruling party - which defied expectations https://www.reuters.com/world/asia-pacific/japan-votes-test-new-pm-kishida-political-stability-2021-10-30 by maintaining a majority in Sunday's parliamentary election - has pledged to double defense spending as public sentiment grows increasingly wary of China.

Japan's military strategy is focused on defending territory https://www.reuters.com/world/asia-pacific/with-an-eye-china-japans-ruling-party-makes-unprecedented-defence-spending-2021-10-13 along the edge of the East China Sea, where it is locked in a dispute with the Chinese government over a group of uninhabited islands. (Reporting by Nicholas P. Brown; additional reporting by Mike Stone, Tim Kelly, Ju-min Park, Sakura Murakami and Kiyoshi Takenaka; Editing by Lincoln Feast.)