US defence secretary Robert Gates said today that the United States would not accept a nuclear-armed North Korea and sternly warned it against transferring any nuclear material.
In a speech to an Asian defence conference in Singapore, Mr Gates also said the threat from North Korea, which this week detonated a nuclear device and launched a series of missiles, could trigger an arms race in Asia.
"We will not stand idly by as North Korea builds the capability to wreak destruction on any target in the region or on us," Mr Gates said. "We will not accept North Korea as a nuclear state."
Meanwhile Russia and Japan have agreed there is a need to respond seriously to the recent nuclear test.
Compounding tensions on the Korean peninsula, a South Korean newspaper quoted a source in Washington as saying Pyongyang was preparing to move an intercontinental ballistic missile from a factory near the capital to a launch site on the east coast.
Increasingly belligerent North Korea has warned of war, saying it was no longer bound by an armistice that ended the 1950-53 Korean War and threatened further provocations in response to UN Security Council censure.
Mr Gates said the Obama administration would hold North Korea "fully accountable" if it transferred any nuclear material outside its borders.
"The transfer of nuclear weapons or material by North Korea to states or non-state entities would be considered a grave threat to the United States and our allies. And we would hold North Korea fully accountable for the consequences of such action."
The statement seemed to harden and broaden the Obama administration's stand on North Korea's recent series of provocations from a regional security issue to a global proliferation threat.
Regional powers are waiting to see what the North might do next after it conducted a nuclear test on Monday. South Korea is on alert on the assessment Pyongyang may make provocative moves using conventional weapons at their heavily armed border.
North Korea has warned of an intercontinental ballistic missile test in anger over UN Security Council punishment for what Pyongyang said was a satellite launch on April 5th.
"Preparations to move an ICBM from the Saneum Weapons Research Centre near Pyongyang by train have been captured by US spy satellites," Saturday's Dong-a Ilbo newspaper quoted a source in Washington knowledgeable about the issue as saying.
The research lab is the North's main centre of research and manufacture of long-range missiles, the newspaper said.
South Korea's defence ministry could not immediately comment on the report.
In New York, the United States and Japan circulated a draft UN Security Council resolution to key members, condemning the claimed nuclear test and demanding strict enforcement of sanctions imposed after the North's first atomic test in October 2006.
Mr Gates said North Korea was not a direct military threat now but said sanctions that bring home "real pain" were needed against Pyongyang.
"If (the North Koreans) continue on a path they are on, I think the consequences for stability in the region are significant and I think it poses the potential, the potential for some kind of an arms race in this region," Gates said.
Western diplomats said permanent Security Council members Russia and China have agreed in principle that North Korea should be sanctioned for its nuclear test, but it was not clear what kind of penalties they would support. Both are generally reluctant to approve sanctions.
"Our hope is that all parties concerned will remain cool-headed and take measures to address the problem," Ma Xiaotian, deputy chief of general staff of the People's Liberation Army, told the Singapore defence conference.
"Our stand on the issue is consistent. We are resolutely opposed to nuclear proliferation. Our view is that the Korean peninsula should move towards denuclearisation."
US officials have urged China to pressure North Korea to step back from nuclear brinkmanship and return to stalled disarmament talks. But many Chinese analysts say Washington overstates Beijing's sway over Pyongyang, as well as their government's willingness to use that influence.
Today, Russian president Dmitry Medvedev and Japanese prime minister Taro Aso agreed on the need to respond seriously to the recent North Korean nuclear test, the Kremlin said.
"The parties shared the view that there is a need to most seriously respond to these steps, representing a challenge to the international security system," the Kremlin said in a statement after a telephone conversation between the two leaders.
The two Koreas have fought two deadly naval clashes on their disputed maritime border in the past 10 years and the North has warned another could happen.
A US defence official said the United States had observed "above average activity" in the past 24 hours at a site in North Korea that has previously been used to test fire long-range missiles.
South Korea's defence ministry said it had seen the number of Chinese fishing boats near the peninsula in the Yellow Sea drop sharply in recent days and is watching the North's activities for indications of aggression.
Meanwhile, the UK's Ministry of Defence confirmed it has sent military aircraft to help verify the strength of a nuclear bomb tested by North Korea.
Examinations are being undertaken by the international community in the area to determine the full strength of the blast and the type of nuclear material used.
The MoD confirmed that a VC10 tanker plane had been sent to Japan to help assist with these verification tests.
The VC10 is typically used for aerial refuelling.
An MoD spokesman said: ¿Following the recent events in North Korea and to support the international community¿s efforts during this time of increased political tension, we can confirm that the UK is supporting in the associated
verification efforts by deploying a VC10 aircraft to Kadena airforce base in Japan."
Reuters, PA