TOKYO, April 14 – US Secretary of State John Kerry on Sunday called on Pyongyang to go back to the negotiating table as he told Japan the United States would protect it from North Korea's threats.

Following a meeting with Japanese Foreign Minister Fumio Kishida in Tokyo, where Patriot missiles have been deployed in anticipation of a missile launch by the North, Kerry pledged the US would backstop its ally.

"The United States is fully committed to the defence of Japan," Kerry told a joint press conference with Kishida.

Kerry's comments came after the Korean Central News Agency said Friday any attempt by Japan to shoot down a missile would result in war that would see Japan "consumed in nuclear flames".

Kerry said Washington and Tokyo were searching for a peaceful resolution, something he described as "our biggest priority".

"The North has to understand and I believe must by now that its threats and provocations are only going to isolate it even further and impoverish its people even further," he said.

"Our choice is to negotiate, our choice is to move to the table and find a way to have peace, and I would hope that whatever fears or considerations the North has... that they would come to the table in a responsible way and negotiate.

"We can find a way to resolve these differences at a negotiating table, and I hope they will hear that."

The Asian leg of Kerry's 10-day tour has seen him move through Seoul and Beijing, with Washington keen to press home the need for a united front against Pyongyang's erratic and bellicose behaviour.

He found a sympathetic ear in Japan, where Prime Minister Shinzo Abe, who will hold talks with Kerry on Monday, said Pyongyang had to realise it was harming itself by being "provocative".

There are fears any launch could come on Monday, the anniversary of the birth of the North's late founder Kim Il-Sung. The presence of Kerry in the region, ensuring maximum publicity, may also appeal to the regime.

"The government will do its utmost to protect the lives and safety of the Japanese people," Abe told local reporters during a visit to Iwo To, better known as Iwo Jima, where he attended a war memorial service.

"The international community has to be united and make North Korea realise that their provocative acts do not bring any benefit to North Korea," Abe said, according to national broadcaster NHK.

During an intense day of diplomacy in Beijing on Saturday, Kerry warned Chinese leaders including President Xi Jinping that the stakes for global and regional security were high.

China is Pyongyang's sole major ally and backer, and is widely seen as the only country with leverage to influence its actions – although it is reluctant to risk destabilising the regime.

The top US diplomat hailed a joint commitment from Chinese and US leaders to work together to dial down the tensions.

"I think that what happened yesterday should not be underestimated and is not a small event in the context of life between China and North Korea.

"What you have is a China that made it very clear that we can't simply have a rhetorical policy. So the question is what steps do you take now so we are not simply repeating the cycle of the past years?

"I believe China, by making clear its policy, will join with others in the effort to make that policy real and implemented."

China's State Councillor Yang Jiechi, who is in charge of Beijing's foreign policy, said his nation "will work with other relevant parties including the United States to play a constructive role".

China is estimated to provide as much as 90 percent of its neighbour's energy imports, 80 percent of its consumer goods and 45 percent of its food, according to the US-based Council on Foreign Relations.

But analysts say it is wary of pushing too hard for fear of a regime collapse sending waves of hungry refugees flooding into China and ultimately leading to a reunified Korea allied with the United States right on its border.

Speaking to journalists later on Sunday, Kerry reiterated his belief that Beijing was a key player and indicated creative thinking was required.

"In the case of North Korea we've spent years in the same dynamic... I'm open personally to exploring other avenues, I particularly want to hear what the Chinese have to say.

"They may have a back channel... I'm not going to be stuck in the mud and an opportunity to get something is flagrantly wasted, because of pre-determined stubbornness. I think you need to keep your mind open."