The Bush administration rejected anew Tuesday direct talks with North Korea and said it would not be intimidated by a reported threat from Pyongyang that it could fire a nuclear-tipped missile unless the U.S. acts to resolve the standoff.

"This is the way North Korea typically negotiates by threat and intimidation," said U.S. Ambassador John Bolton. "It's worked for them before. It won't work for them now."

The White House said, meanwhile, there is a "remote possibility" that the world never will be able to fully determine whether North Korea succeeded in conducting a nuclear test Monday. While acknowledging that the action was provocative, White House press secretary Tony Snow suggested that it's possible that the test was something less than it appeared.

"You could have something that is very old and off-the-shelf here, as well, in which case they've dusted off something that is old and dormant," he said. The comment appeared to indicate that the White House was attempting to downplay the significance of the test, but Snow said later that he was merely posing a hypothetical question.

While Democrats claimed the test was evidence of a failed U.S. policy, Snow argued that the test has left the nations involved in the six-party negotiations with the communist regime more unified and determined to convince Pyongyang incentives to give up its nuclear weapons ambitions. He also denied that the demands of the war in Iraq hampered the Bush administration's ability to dissuade North Korea from developing nuclear weapons.

"The Chinese, the South Koreans, the Japanese — they all have more direct leverage over the North Koreans than we do," Snow said. "The people who have the greatest ability to influence behavior are now fully invested in equal partners in a process to deal with the government of North Korea."

CountryWatch: North Korea

North Korea stepped up its threats, saying it could fire a nuclear nuclear-tipped missile unless the U.S. acts, the Yonhap news agency reported Tuesday from Beijing. But even if Pyongyang is confirmed to have nuclear weapons, experts say it's unlikely the North has a bomb design small and light enough to be mounted atop a missile.

Asked about the Yonhap report, Bolton said, "Well, I think it's been perfectly obvious for quite some time that North Korea has been seeking a delivery capability for its nuclear weapons. It's one reason why as far back as 2001, President Bush led the effort to get the United States out from under the restrictions of the Anti-Ballistic Missile Treaty, so we could build missile defense against precisely this kind of threat."

In response to North Korea's purported nuclear test, the United States is pressing at the United Nations for stringent sanctions on Pyongyang, including a trade ban on military and luxury items, the power to inspect all cargo entering or leaving the country, and freezing assets connected with its weapons programs.

Meanwhile, Democratic New Mexico Gov. Bill Richardson, a former U.S. ambassador who has visited North Korea, said the Bush administration should abandon its long-standing refusal to engage in direct talks with North Korea. He said President Bush was right to seek sanctions against North Korea in the U.N., but should next move to direct talks with the reclusive nation.

In taking that stance, Richardson echoed the message that former Secretary of State James A. Baker III said Sunday, as Baker urged the administration to talk directly to adversaries around the world.

The administration has been attempting for years to get more countries to join its anti-proliferation initiative, aimed at stopping countries like North Korea from selling nuclear weaponry and missiles. But it has refused one of North Korea's key demands: that the United States engage in direct one-on-one talks. Instead the administration insists on sticking to the so-called six-party format, where Russia, China, South Korea and Japan have joined the United States in talking to North Korea.

Bolton, interviewed on CNN and on CBS' "The Early Show," said that if North Korea wanted to talk with the U.S., it needed to rejoin the six-party talks.

"If they want to talk to us, all they have to do is buy a plane ticket to Beijing," where the talks have been stalled for months, Bolton said. "The North Koreans can talk to us anytime they want on a bilateral basis if they come back to the six-party talks, which they have been boycotting."

Bolton cast the standoff with Pyongyang as one "between North Korea and the rest of the world" that will result in sanctions or more if the rogue nation does not restart talks with the international community.

Asked about the possibility of U.S. military action against North Korea, including a possible naval blockade, Bolton said, "Well, we're not at that point yet."

"We keep the military option on the table because North Korea needs to know that, but President Bush has been very clear he wants this resolved peacefully and diplomatically," Bolton said.