Japan subs 'superior' US believe: adviser

Tony Abbott's former national security adviser has suggested the US would prefer Australia award a multi-billion dollar submarine contract to Japan.

Andrew Shearer, writing in The National Interest magazine, says the US has been careful not to take sides in the competition between France, Germany and Japan to win the contract.

"But senior US officials and military officers are in no doubt both as to the superior capability of the Japanese Soryu class and to the long-term strategic benefits to the United States and the region of an interoperable fleet of Australian and Japanese conventional submarines equipped with US combat systems."