"There is no reason for the DPRK to stay away from the diplomatic process and my government is very much committed to these talks," said Hill, referring to the North by its official name, the Democratic People's Republic of Korea.

The US assistant secretary of state for East Asia and Pacific affairs voiced concern about media reports that Pyongyang, which claims to have built nuclear weapons, may be preparing an underground nuclear test.

"I think all governments in the world have made very clear that it would be a very unwelcome development, and that the DPRK should really think long and hard for it to take such a provocative step.

"I hope the DPRK will understand that their future lives are not with these tests but by coming to the negotiating table and implementing the September agreement," he said.

Hill will also visit China and South Korea during his swing through the region, which he said was part of regular consultations.

The North agreed in principle in September last year to give up its nuclear weapons program in exchange for aid and security guarantees but walked out of talks two months later to protest US sanctions on a Pyongyang-linked bank.

The United States has been negotiating with the communist state through six-way talks that also include China, Japan, Russia and South Korea.

Hill, who last visited the region in July after North Korea defied international appeals by test-firing seven missiles, said there were no new incentives on the table for the reclusive Communist state.

"We're not proposing incentives to North Korea to come back to the talks," he said, noting that an agreement had already been reached last year.

"All six parties agree to that and I don't think any party should be giving incentives to another party to come and implement what everyone's agreed to," Hill added.

The North on Saturday accused the United States of threatening war with a test of its missile defense system and joint military exercises with South Korea.

The semi-official Committee for Peaceful Reunification of the Fatherland called the military drills, which ended on Friday, "little short of a declaration of war against the DPRK."

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