Japanese Prime Minister Shinzo Abe has expressed concern over China's possible use of force in the disputed East Sea.

While Mr Abe said Japan will work with ASEAN to ensure that the rule of law be respected in settling territorial disputes, he also argued that such tensions highlight the need for Japan to expand the role of its Self Defense Force.

China's military buildup is topmost on Mr Abe's mind when it comes to securing Japan.

Speaking in Parliament about his plans to expand the role of the country's Self-Defense Force, Mr Abe highlighted that China has increased its military budget by almost four times in the last 10 years.

Its budget for this year is US$132 billion.

That's more than two-and-a-half times Japan's US$49 billion budget.

Mr Abe is concerned this would increase the possibility of China using force in the disputed East Sea - something he warned China against.

"China is looking to change the status quo in the East Sea through the use of force. We will work with ASEAN countries to assert that the rule of law should be respected," he told Parliament.

China claims almost the entire East Sea, rejecting rival claims to parts of it from Vietnam, the Philippines, Malaysia and Brunei.

It also has a separate maritime dispute with Japan over islands in the East China Sea.

Japan's security pact with the US does cover the disputed region, but Mr Abe sees Japan and the US as equal partners in this alliance, and argues that its Self-Defense Force capabilities need to be boosted.

He also stated that the current interpretation of the constitution prevents Japan from protecting vessels that are not their own, thereby limiting its effectiveness.

Mr Abe also revealed that the Philippines and Vietnam have asked Japan to supply them with coastguard vessels amid the rising tensions with China.

But he said Japan was currently not able to help, as it needed the vessels to protect its own sea-lane.

Despite his firm stance on the need to expand the role of the Self-Defense Force, Mr Abe wasn't clear on what that would mean, as his party has not yet come to an agreement with its coalition partner, the pacifist New Komeito, on what is permitted in the context of collective self defence.

CNA/ir