John Bolton, undersecretary of state for arms control and international security, met with Yoon as South Korea denied the existence of a rift with the United States on Washington's drive to bring the nuclear crisis to the United Nations.

Bolton, considered a hawk on North Korea, earlier insisted that Pyongyang's nuclear violations be brought before the UN Security Council, a move certain to infuriate Pyongyang.

South Korea's Foreign Ministry said Seoul was not opposed to a UN role but took issue with the timing, saying efforts to resolve the crisis through negotiations should be exhausted first.

"We are now exerting our efforts for a diplomatic solution. It is better for us to resolve the crisis outside the UN framework at this time," said ministry spokesman Kim Sun-Heung.

Two previous attempts to engage the UN in the crisis have been thwarted by China and Russia, permanent Security Council members who have argued in the past that UN intervention could deepen the standoff.

The UN's atomic watchdog, the International Atomic Energy Agency, ruled North Korea in "non-compliance" with its non-proliferation obligations in January and recommended the matter be referred to the world body for possible sanctions. North Korea has said that any UN sanctions would mean war.

Bolton arrived from China Tuesday for a three-day stay in Seoul before heading for Tokyo on the third and final leg of his Asia swing on Thursday.

In Seoul he is also scheduled to meet with President Roh Moo-Hyun's national security advisor Ra Jong-Yil and foreign policy advisor Ban Ki-Moon.

His visit comes as Chinese-led efforts to bring North Korea to the negotiating table for multilateral talks to end the nine-month old nuclear crisis appear to have stalled.

A senior official here said North Korea was considering the latest proposal from the United States for three-way talks that would be followed immediately by expanded five-party, or even six-party talks.

However, North Korea, through its official media, reverted to its insistence on a non-aggression pact and one-on-one talks, which Washington has ruled out.

"It is the stand of the DPRK (North Korea) that the bilateral talks should be held between the DPRK and the US to be followed by the US-proposed multilateral talks in order to settle the nuclear issue between Pyongyang and Washington," Pyongyang's official Korean Central News Agency said.

The dispatch denounced as "unacceptable" Washington's demand that North Korea scrap its nuclear weapons ambitions prior to substantive dialogue and reiterated North Korea's own demand for a non-aggression pact.

The demand for a non-aggression pact represented a major hurdle to progresss, according to Roh's national security adviser Ban.

"If North Korea keeps insisting on having a non-aggression treaty signed with the United States, there would be rough sailing for negotiations," he said in a radio interview.

The nuclear crisis was triggered in October when Washington revealed that Pyongyang was running a nuclear programme in violation of a 1994 arms control accord.

North Korea kicked out IAEA inspectors late last year and then withdraw from the Nuclear Non-Proliferation Treaty. It has since claimed it has reprocessed 8,000 spent nuclear fuel rods after reopening its nuclear complex at Yongbyon, north of Pyongyang, frozen under 1994 accord.

During his last visit here in January Bolton said the 1994 deal, known as the agreed framework, was a dead letter.

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