US urges North Korea to get 'serious' on talks
It is time for North Korea to get "serious" about negotiations for peace, the US Defence Secretary Robert Gates has said.
Mr Gates was speaking in Japan, after a four-day visit to China.
He said the risk of provocation leading to war between the two Koreas was very high and noted the South had the right to respond if attacked.
Mr Gates's trip has focused on repairing military ties with China and easing tensions between the Koreas.
His meeting with the Japanese Prime Minister Naoto Kan was also an opportunity to reaffirm the US-Japan alliance, amid recent tensions over the stalled relocation of a US base in Okinawa.
Speaking at a news conference, Mr Gates said there was a "common interest" between the US, China, South Korea and Japan in securing peace and stability on the Korean peninsula.
"There must be concrete evidence that they are finally serious about negotiations," Mr Gates said of the leadership in Pyongyang.
"It's a long-standing principle that every country has the right to protect itself and defend itself against an unprovoked attack," Mr Gates added.
"The objective that we all have in common is how do we prevent another provocation from taking place?"
North Korea has offered talks, and the reopening of tourism and industrial projects in recent days, but South Korea, the US and Japan have responded sceptically.
They remain insistent that the North must apologise for its shelling of a southern island in November and the sinking of a South Korean warship last March - an incident in which Pyongyang denies any role.
Speaking in Washington, US Joint Chiefs of Staff Chairman Mike Mullen said North Korea posed "an evolving threat, not just to the region but to the United States specifically".
He said North Korea's capability to strike beyond its shores was "becoming more and more dangerous".
Mr Gates had spoken earlier, in China, about how North Korean missiles could pose a direct threat to the United States within five years.
He had also noted what he called a "sea change" in attitudes in South Korea towards the North, with far less patience in evidence for the North's behaviour.
On Okinawa, Mr Gates sought to play down tensions saying the US-Japan alliance was broader than any single issue.
"We hope to move forward with the relocation of US forces in Okinawa in ways that are more appropriate to our strategic posture while reducing the impact on the communities nearby," Mr Gates said.
The US wants to build a new air base in northern Okinawa, closing the controversial Futenma base in crowded central Okinawa.
But there is widespread opposition to the plan in Okinawa from residents who say the island hosts far more than its fair share of the US military presence in Japan.
Mr Gates will leave Japan for South Korea on Friday.