US Secretary of State John Kerry en route to Japan

US Secretary of State John Kerry (L) and South Korean President Park Geun-hye have a private bilateral meeting at Blue House in Seoul. Credit: REUTERS/Paul J. Richards/Pool (SOUTH KOREA

US Secretary of State John Kerry was en route to Japan, the last stop on an Asian tour aimed at reining North Korea's nuclear ambitions.

Kerry met China's top leaders on Saturday in a bid to persuade them to push reclusive North Korea, whose sole main ally is Beijing, to return to nuclear talks after weeks of threats of nuclear attacks on the United States and South Korea.

Also likely to be high on the agenda in talks in Tokyo are Japan's territorial disputes with China and the future of US bases in Japan.

The US and Japan this month announced an agreement for the return to Japan of a US air base, taking a step to resolving an issue that trouble relations.