Kerry urges North Korea to join regional dialogue
US Secretary of State John Kerry has called on North Korea's leaders to "come to the table in a responsible way" to end regional tensions.
Speaking in Tokyo, the fourth and final stop on his Asian tour, Mr Kerry warned North Korea it risked further isolation if its threats continued.
He also reaffirmed the US commitment to defend its allies, including Japan.
The countries he had visited were united in seeking the denuclearisation of the Korean peninsula, he said.
On Friday Mr Kerry visited South Korea, and on Saturday he was in China, whose leaders he has said are "very serious" in their pledge to help reduce tensions - and to help end the North Korean nuclear programme.
North Korea has recently threatened attacks against South Korea and the US, sparking alarm in the region.
Speculation has been building that the North is preparing a missile launch, following reports that it has moved at least two Musudan ballistic missiles to its east coast.
Japan is within range of these rockets and has been taking precautions, including setting up batteries of US-made Patriot anti-missile systems around the capital and sending two warships to the Sea of Japan, with orders to shoot down any missiles fired towards the Japanese islands.
At a joint news conference with Foreign Minister Fumio Kishida, Mr Kerry said North Korea had to understand by now "that its threats and provocations are only going to isolate it further and impoverish its people even further".
"The US will do what is necessary to defend our allies against these provocations, but our choice is to negotiate," he said.
"We would hope that whatever considerations and fears the North has of the US or others in the region they would come to table in responsible way and negotiate that."
Mr Kerry stressed that Seoul, Beijing, Tokyo and Washington had "committed to take action together" and to "making that goal of denuclearisation a reality".
Mr Kishida said their role was to persuade North Korea that its aggressive behaviour "will not benefit them in any way whatsoever" and that the international community had to send out this strong message.
Washington and Tokyo have a security alliance dating back to the 1950s, under which Washington is bound to protect Japan if it is attacked.
Kaesong offer rejected
North Korea habitually issues fiery statements denouncing the US and South Korea, but the rhetoric has grown increasingly aggressive since the UN imposed a fresh round of sanctions in March.
The sanctions punished Pyongyang for carrying out a banned test of a ballistic missile and conducting its third test of a nuclear device.
Pyongyang has also been angered by joint military manoeuvres by the US and South Korea, which it says are preparations for war.
It has responded by vowing to restart an inactive nuclear reactor, shut an emergency military hotline to the South and by urging countries to withdraw their diplomatic staff, saying it cannot now guarantee their safety.
It has also withdrawn North Korean workers from the Kaesong industrial complex - a rare joint Korean enterprise where South Korean companies employed Northerners.
The South has offered to discuss the future of the complex, but on Sunday Pyongyang rejected this, saying it was an "empty, meaningless" act aimed at disguising invasion plans, the North's KCNA state news agency reports.
On Monday, North Korea will mark the birth of national founder Kim Il-sung. Such occasions are traditionally marked with shows of military strength and it is thought this year the date could be used for a missile launch.
Some estimates suggest that the Musudan missiles which North Korea has moved to its east coast could travel 4,000km (2,500 miles).
That would put US bases on the Pacific island of Guam within range, although the exact threat is unclear as it is not believed that the Musudan has been tested before.
Mr Kerry has stressed that it would be a "huge mistake" for the North to go ahead with a launch, saying it would further isolate North Korea and that the people of the country are in need of food, not missiles.