WASHINGTON: The United States said Friday it was open to sending an envoy to Pyongyang but insisted that North Korea prove it is serious about giving up nuclear weapons for good.

North Korea has stepped up pressure on the United States to agree to meet one-on-one, announcing this week it had produced more bomb-making plutonium.

Jeff Bader, the senior director for East Asian Affairs on the White House's National Security Council, said the United States wanted proof the communist state was committed to six-nation denuclearization talks.

"If we see that, then there is no problem with bilateral contacts either in Pyongyang or elsewhere," Bader said at the Brookings Institution ahead of Obama's trip to Asia next week.

"We're less interested in process than we are in outcome," he said.

Two newspapers, South Korea's Hankyoreh and Japan's Yomiuri Shimbun, have quoted unnamed sources saying that Stephen Bosworth, the US special representative on North Korea, has agreed to go to Pyongyang in late November.

Bader said no such decision had been made.

The United States has periodically sent envoys on short visits to Pyongyang. Former president Bill Clinton went in August to free two US reporters, although officials called it a private trip.

North Korea in April bolted from a six-nation disarmament agreement and a month later staged a second atomic weapons test, leading the United Nations to slap tougher sanctions at US urging.

But North Korean leader Kim Jong-Il said last month he was willing to go back to the six-party talks depending on the outcome of bilateral discussions with the United States to repair "hostile relations."

Bader repeated the US stance that Washington was ready to meet one-on-one with North Korea but only "in the context" of six-party talks.

"We want to see genuine signs that the North Koreans understand that the six-party process is the right framework" and that they are bound by earlier agreements, Bader said.

The six-party talks -- grouping China, Japan, the two Koreas, Russia and the United States -- reached agreements in 2005 and 2007 under which Pyongyang would drop its nuclear program in return for badly needed aid and security guarantees.

US officials said that they wanted North Korea to close down its nuclear program for good -- not just another temporary closure of the communist state's Yongbyon nuclear facility.