In a meeting with Defence Minister Toshimi Kitazawa, Gates "suggested Japan consider three US planes to upgrade their fleet," the F-35 Joint Strike Fighter, the F/A-18 Hornet and the F-15 Eagle, the senior defence official told AFP.

Gates offered that the Pentagon could provide Japan with an analysis of the merits of each aircraft, said the official, who spoke on condition of anonymity.

Japan is taking stock of its defence hardware in the face of China's growing military might and assertive stance in the Pacific.

"And so that would give Japan the opportunity -- if they bought the right airplane -- to have a fifth generation capability. And I might have a few suggestions for them," he told reporters on Tuesday.

"Fifth-generation" fighters are equipped with stealth, radar-evading equipment, and the F-35 -- which is still under development -- would meet that requirement.

Lockheed Martin's F-35, the most expensive weapons programme in Pentagon history, has been plagued by cost overruns and technical delays, with the project expected to cost an estimated $382 billion.

The United States is covering 90 percent of the cost of the F-35's development but has participation from Britain, Italy, Turkey, the Netherlands, Canada, Denmark, Norway and Australia.

Other nations, including Israel and Singapore, have signed contracts to buy the aircraft.

Japan initially aimed to acquire the F-22 stealth fighter to replace its ageing F-4EJ fighter fleet, but US law prohibits exports of the F-22 and the United States has announced a plan to halt production of the model.

Japan has also studied other models such as the F/A-18 and F-15FX, and the Eurofighter, produced by a consortium of European manufacturers, as possible replacements for its fighter fleet.