The US will never accept North Korea as a nuclear power and will come to the defence of the South if necessary, secretary of state John Kerry said after meeting his counterpart in Seoul this morning.
"We are all united in the fact that North Korea will not be accepted as a nuclear power," Kerry told a press conference.
Kerry was in Seoul ahead of a visit to China and Japan in a bid to rein in North Korea's nuclear ambitions after more than a month of threats from Pyongyang that it would strike at the US and South Korea if attacked.
Meanwhile, a Pentagon spy agency report concluded for the first time that North Korea likely has a nuclear bomb that can be launched on a missile, but US defence and intelligence officials have cast doubt on Pyongyang's atomic weapons capabilities.
Illustrating the high stakes surrounding the escalating tensions on the Korean peninsula, a study by the Pentagon's Defense Intelligence Agency stoked fears that North Korea could be closer to being able to launch a nuclear missile.
Secret assessment
The secret assessment, mistakenly marked as unclassified and partially revealed at a congressional hearing yesterday, said the agency had "moderate confidence" that North Korea possessed nuclear weapons that could be fitted onto ballistic missiles. But it said any such missile would probably be unreliable.
The evaluation, dated last month, was made public by Republican Representative Doug Lamborn as he questioned senior Pentagon officials about North Korea's nuclear weapons programme during a hearing of the House of Representatives Armed Services Committee.
"DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles, however the reliability will be low," said Mr Lamborn. He was quoting from a DIA report entitled "Dynamic Threat Assessment 8099: North Korea Nuclear Weapons Program (March 2013)."
US officials and South Korea sought to play down the DIA evaluation.
"It would be inaccurate to suggest that the North Korean regime has fully tested, developed or demonstrated the kinds of nuclear capabilities referenced in the passage," said Pentagon spokesman George Little.
James Clapper, the country's senior intelligence official, warned that the assessment was not necessarily shared by the wider US intelligence community.
"I would add that the statement read by the member is not an Intelligence Community assessment. Moreover, North Korea has not yet demonstrated the full range of capabilities necessary for a nuclear armed missile," Clapper, the director of national intelligence, said in a statement.
Raising tension
But the release of part of the DIA report will likely raise tension on the Korean peninsula, where North Korea has stationed as many as five medium-range missiles on its east coast, according to assessments by Washington and Seoul, possibly in readiness for a test-launch that would demonstrate its ability to hit US bases on Guam.
General Martin Dempsey, chairman of the US Joint Chiefs of Staff, declined to comment as he had not seen the DIA report, suggesting it was not a major part of the military's thinking as it beefed up anti-missile defenses around the Pacific in the face of threats of war from North Korea in recent weeks.
South Korea's defence ministry said it did not believe North Korea had succeeded in readying a nuclear warhead for a missile, a process known as "miniaturising".
Mr Lamborn did not say what range any nuclear-capable North Korean missiles might have. Kristensen said one analyst recently claimed nuclear warhead capability for North Korea's Nodong short- to medium-range missile. It would be able to hit US-based facilities in the region, including South Korea and probably Japan.
The United States and South Korea have plans to respond proportionately to North Korean provocations like the shelling of an island or attacking a ship.
But not wanting to increase the tension in Korea, Washington has not been explicit about how it would respond to an incident involving nuclear arms, beyond saying it was capable of defending itself and its partners.
President Barack Obama said yesterday the US would work diplomatically to reduce tensions with North Korea, but warned that Washington would take "all necessary steps" to protect America and its allies.
The US has revamped its missile defence plans and positioned two guided-missile destroyers in the Western Pacific recently.
In the latest move, the Pentagon is to deploy a Terminal High Altitude Area Defense system to Guam in the coming weeks after adding 14 new anti-missile interceptors in Alaska.
Most observers say Pyongyang has no intention of starting a war that would likely bring its own destruction, but they warn of the risks of miscalculation.
Using persuasion
Meanwhile, besides Mr Kerry’s stops in South Korea and Japan, he will also visit China to urge officials there to persuade North Korea to abandon its nuclear weapons programme, according to a senior State Department official traveling with him.
Asia is the final leg of Mr Kerry's six-nation trip, which has taken him to Turkey, Israel and Britain, where he attended the G8 meeting yesterday in London.
His trip comes as the government of Kim Jong-un has apparently been making preparations to conduct a test launching of a medium-range Musudan missile with a potential range of 2,500 miles.
The State Department official said the US wanted China to crack down on the illicit flow of funds that move through front companies and banks which the North Korean government uses to support its nuclear weapons programme.
"We want to see them do what we do, what the Japanese do, what the South Koreans do, which is to stick to UN Security Council resolutions," the official said, and "stop those money trails".
The second step the US wants the Chinese to take is to "carry some tough message to Pyongyang and make it clear to them that denuclearisation is also their goal," the official said.
A working assumption in the US is that Mr Kim's recent bellicose statements and sabre-rattling is intended to shore up his power at home and assure the North Korean military that it will retain the first claim on resources - what policy analysts call the "military first" policy.
"His real goal, of course, is regime survival," the State Department official said. "So I still believe that is the ultimate goal and that is what he is trying to do."
Reuters/New York Times