John Bolton said the threat of a missile launch was no way to seek discussions.

"You don't normally engage in conversations by threatening to launch intercontinental ballistic missiles," he said on Wednesday.

Bolton said they could not agree to talks as it would simply encourage North Korea to negotiate this way in the future. He warned he was holding discussions with the Security Council members on possible action if North Korea decides to test a missile.

Adam Ereli, US state department deputy spokesman, echoed Bolton's comments, saying direct talks with North Korea are "not on the cards".

Ereli reiterated the US position that any discussions should be in the framework of the six-party talks on North Korea's nuclear programme, involving the two Koreas, the US, China, Japan and Russia. Washington is calling for North Korea to return to the talks, which are stalled over a US crackdown on the North's alleged illicit financial activity.

Earlier on Wednesday, Han Song Ryol, deputy chief of North Korea's mission to the UN, said in reported remarks that Pyongyang was seeking to resolve the possible missile test concerns through talks.

"North Korea as a sovereign state has the right to develop, deploy, test fire and export a missile," he said. "We are aware of the US concerns about our missile test-launch. So our position is that we should resolve the issue through negotiations."

North Korea test-fired a missile over Japan into the Pacific Ocean in 1998, and reports that it was preparing another test have drawn warnings of a tough response from both Tokyo and Washington.

Bush warning

From the Austrian capital Vienna, George Bush, speaking after talks with European Union leaders, warned North Korea against firing a missile.

"North Koreans have made agreements with us in the past and we expect them to keep their agreements," Bush said on Wednesday.

"For example agreements on test launches, we think it would be in the world's interest to know what they're testing, what they intend to do on their test."

Intelligence reports say North Korea has fuelled a Taepodong-2 missile with a range experts estimate could be up to 15,000km - making it capable of reaching parts of the US.

The US has activated a ground-based interceptor missile-defence system in case Pyongyang goes ahead with a launch.

US policy criticised

In related news, a former US diplomat who was deeply involved in North Korea policy, said the Bush administration's approach has been a failure, leaving Pyongyang free to pursue its nuclear and missile programmes.

One fundamental failure of Bush's approach was the tendency to raise tensions and make South Korea anxious by stating that "all options" were the table, a phrase underscoring US intentions to use force against North Korea if necessary, David Straub, retired head of the state department's office of Korean affairs, said.

Straub said the only viable US approach is serious negotiations, the appointment of a high-level envoy and a willingness to engage in bilateral as well as multilateral talks, something the Bush administration has avoided.