TOKYO - US Secretary of State John Kerry on Sunday stressed the United States is willing to engage with the Democratic People's Republic of Korea (DPRK) as long as it takes steps to give up nuclear weapons.

He also vowed the United States would protect its Asian allies against any provocative acts by the North, but said Washington wants a peaceful solution to rising tensions in the region.

"We are prepared to reach out but we need (the) appropriate moment, appropriate circumstance," Kerry said, adding that DPRK had to take steps towards giving up its nuclear programs.

"They have to take some actions. Now how many and how much I want to have a discussion with folks back in Washington (about)... but they have to take action," Kerry told a small group of reporters.

The North has threatened for weeks to attack the United States, the Republic of Korea(ROK) and Japan since new UN sanctions were imposed in response to its latest nuclear arms test in February. Speculation has mounted of a new missile launch or nuclear test.

"I think it is really unfortunate that there has been so much focus and attention in the media and elsewhere on the subject of war, when what we really ought to be talking about is the possibility of peace. And I think there are those possibilities," Kerry earlier told a news conference in Tokyo after a meeting with his Japanese counterpart, Fumio Kishida.

Kerry was in Japan for the final stop on an Asian tour aimed at solidifying support for curbing DPRK's nuclear program, and reassuring US allies.

Kerry said the United States would "do what was necessary" to defend its allies Japan and ROK, but added: "Our choice is to negotiate, our choice is to move to the table and find a way for the region to have peace."

Kerry also sought to clarify his comments made in Beijing on Saturday, which some took to suggest he might be offering to remove recently boosted missile defence capabilities in Asia if China persuaded DPRK to abandon its atomic programs.

The Pentagon in recent weeks has announced plans to position two Aegis guided-missile destroyers in the western Pacific and a Terminal High Altitude Area Defence (THAAD) missile defence system to Guam.

"The president of the United States deployed some additional missile defense capacity precisely because of the threat of DPRK. And it is logical that if the threat of DPRK disappears because the peninsula denuclearises, then obviously that threat no longer mandates that kind of posture. But there have been no agreements, no discussions, there is nothing actually on the table with respect to that," Kerry said.

Japan's Kishida told the same news conference that the two allies want Pyongyang to abandon its nuclear ambitions.

"We agreed that DPRK should cease provocative speech and behaviour and show it is taking concrete action toward denuclearisation," he said. "We cannot allow DPRK in any way to possess nuclear weapons."

DPRK Unbending

Pyongyang, which was preparing to celebrate the birth date of state founder Kim Il-sung on Monday, reiterated it had no intention of abandoning its atomic arms programs.

"We will expand in quantity our nuclear weapons capability, which is the treasure of a unified Korea ... that we would never barter at any price," Kim Young-nam, DPRK's titular head of state, told a gathering of officials and service personnel applauding Kim Il-sung.

The KCNA news agency also rejected as a "cunning trick" ROK's President Park Geun-hye's suggestion last week of holding talks with the North.

The South Korean capital, Seoul, displayed the calm it has shown throughout the crisis. Residents strolled in bright sunshine a day after the city's World Cup stadium was jammed with 50,000 mostly young fans of local rapper Psy.

On Saturday, Kerry met leaders in China, the North's sole diplomatic and financial benefactor, and said China and the United States were committed to "the denuclearisation of the Korean peninsula in a peaceful manner".

During his first stop in ROK, where the United States has 28,000 troops stationed, Kerry said DPRK, furious at joint US-ROK military drills, would be making a "huge mistake" if it were to launch a missile.

He also said China was in a position to influence the North's policy and had to put "some teeth" into efforts to persuade Pyongyang to alter its policies.

Japan, separated from DPRK by less than 1,000 km (625 miles) of water and a frequent target of its anger, is well within range of DPRK's medium-range missiles.

Japanese news reports said Tokyo had sent Aegis-class destroyers capable of missile interception to the Sea of Japan. Patriot Advanced Capability-3 interceptor missiles have been deployed at key locations in the capital and surrounding areas.

Kerry's agenda in Tokyo also included Japan's territorial disputes with China, and the future of US bases in Japan.

He repeated that while Washington took no position about the ultimate sovereignty of tiny isles in the East China Sea claimed by both China and Japan, the United States "opposed any unilateral action that would somehow change the status quo".

A flare-up of the territorial row has raised fears of an unintended military incident near the islands, known as the Senkaku in Japan and the Diaoyu in China. The United States says the islets fall under a US-Japan security pact, but is keen to avoid a clash in the economically vital region.