TOKYO - US President Barack Obama vowed Thursday to defend Japan if China attacks over a tense territorial dispute, but also urged Beijing to help stop North Korea from forging ahead with its "dangerous" nuclear programme.
Obama described as "critically important" China's role in keeping its wayward ally in check after South Korea said heightened activity at the North's main nuclear test site could point to an imminent test -- its fourth.
"China's participation in pushing the DPRK (North Korea) in a different direction is critically important," the president told a joint press briefing with Japanese Prime Minister Shinzo Abe.
"It is the most destabilising, dangerous situation in all of the Asia-Pacific region."
Despite his call for China's help, Obama also underlined US support for Japan, saying that islands at the centre of its bitter territorial dispute with Beijing are covered by a defence treaty that would oblige Washington to act if they were attacked.
"Article five (of the US-Japan security treaty) covers all territories under Japan's administration including (the) Senkaku islands," he said, referring to the East China Sea archipelago which Beijing calls the Diaoyus.
"We do not believe that they should be subject to change unilaterally, and what is a consistent part of the alliance is that the treaty covers all territories administered by Japan."
Obama added that "this is not a new position" and "there's no red line that's been drawn".
"We stand together in calling for disputes in the region, including maritime issues, to be resolved peacefully through dialogue," he said.