TOKYO - JAPAN should raise its military spending as other countries in the region do, and share the costs of defending itself with the United States, Washington's ambassador to Tokyo said on Tuesday.

Ambassador Thomas Schieffer said Japan, whose defence is largely covered by the United States under a bilateral security treaty, spends roughly the same amount on its military as it did in 1998.

In contrast, the US defence budget had nearly doubled from 1998 to 2007, while China, South Korea and Russia were also increasing military spending, he said.

'And we believe that Japan should consider the benefits of increasing its own defence spending to make a greater, not lesser, contribution to its own security.'

Japan is home to nearly 50,000 US military personnel who are obliged to defend Japan under the two allies' security treaty.

Japan has an unofficial cap on defence spending that limits its budget to less than 1 per cent of its gross domestic product (GDP), and in addition the government is focused on trimming its huge public debt.

Japan's defence-related budget for the fiscal year from April was set at 4.78 trillion yen (S$62.7 billion), down 0.5 per cent from a year earlier. Mr Schieffer said the spending ratio to GDP this year could turn out to be as low as 0.89 per cent.

Japan's pacifist constitution prohibits the maintenance of a military, although it has been interpreted to allow armed forces for self-defence.

Mr Schieffer also said the two allies should improve the way they procure weapons, for example by having Japan buy a fighter jet that complements US fighters.