Diplomats from the United States, South Korea and Japan met in Seoul today to discuss policy responses to North Korea's accelerating efforts to expand its nuclear weapons programme.
Before flying to Seoul for talks with South Korean vice foreign minister Lim Sung-nam, US deputy secretary of state John Sullivan and Japanese deputy foreign minister Shinsuke Sugiyama met in Tokyo on Tuesday and vowed to find more ways to apply pressure on Pyongyang.
The vice-ministerial discussions will be followed by a meeting between the countries' top envoys for the currently-stalled nuclear disarmament talks with North Korea that also involved China and Russia.
North Korea has been rejecting the six-party meetings since 2008.
The talks came as the United States and South Korea held joint naval drills involving fighter jets, submarines and other naval vessels, including the aircraft carrier USS Ronald Reagan, to train for potential North Korean provocations. The allies regularly conduct joint exercises that Pyongyang condemns as invasion rehearsals.
North Korea in recent months has tested purported thermonuclear weapons and long-range missiles and flew two powerful new mid-range missiles over Japan between threats to fire the same weapons toward Guam, a Pacific US territory and military hub.
After his meeting with Mr Sugiyama in Tokyo on Tuesday, Mr Sullivan said that the focus at the State Department was still on diplomacy to solve the problem and eventually denuclearise the Korean Peninsula.
"We must, however, with our allies in Japan and South Korea and elsewhere, be prepared for the worst should diplomacy fail," he said, adding that the United States must be prepared to defend itself and its allies.
South Korean foreign ministry spokesman Noh Kyu-duk said ahead of the Seoul meetings that the allies were committed to "stably managing the situation" and pursuing all available avenues for North Korea's denuclearisation, including efforts to bring Pyongyang back to the negotiating table.
North Korea's deputy UN ambassador, Kim In Ryong, said Tuesday at the United Nations that his country planned to conduct more satellite launches, which outside governments see as a cover for banned tests of missile technologies.
On Monday, Mr Kim told the UN General Assembly's disarmament committee that the situation on the Korean Peninsula had "reached the touch-and-go point and a nuclear war may break out any moment", citing the US-South Korea drills and what he called US plans to remove the North's leadership.
He said the North had the right to possess nuclear weapons in self-defence because it was under the direct nuclear threat of the United States.