China agreed Tuesday that North Korea must be punished for testing a nuclear device, but sought to soften a U.S. and Japanese sanctions plan that it said would be too crushing for its impoverished ally.

The debate over sanctions began at the U.N. as scientists and governments suggested that the underground test on Monday was a partial failure, producing a smaller blast than had been planned.

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The Bush administration asked the U.N. Security Council to impose a partial trade embargo including strict limits on Korea's profitable weapons exports and freezing of related financial assets. All imports would be inspected too, to filter out materials that could be made into nuclear, chemical or biological weapons.

The United States reiterated that it would not talk with the North Koreans one-on-one, but Secretary of State Condoleezza Rice assured the North that the U.S. would not attack.

Rice rejected a suggestion that Pyongyang may feel it needs nuclear weapons to stave off an Iraq-style U.S. invasion. President Bush, she told CNN, has told "the North Koreans that there is no intention to invade or attack them. So they have that guarantee. ... I don't know what more they want."

U.S. Ambassador John Bolton sounded upbeat after Tuesday's round of talks at the Security Council, but said differences remained in advance of Wednesday's meeting.

"Look, we don't have complete agreement on this yet, that's hardly a news flash, but we're making progress and we're I think at a point we can try and narrow some of the differences we do have," Bolton said.

China, which reacted to Monday's blast with a strong condemnation but considers North Korea a useful buffer against U.S. forces stationed in South Korea, said it envisioned only a limited package of sanctions — not what the United States and especially Japan were demanding.

China and Russia object to plans to interdict shipments and block financial transactions. They also oppose a new suggestion that Japan proposed Tuesday — to include mention of the North's abduction of Japanese citizens in the 1970s and '80s.

"We certainly understand that Japan is close to the country. But I think you cannot ask by this resolution to kill a country," China's U.N. Ambassador Wang Guangya told The Associated Press. He said the Security Council must impose "punitive actions" but that they have to "be appropriate."

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Though far less than what the Americans and Japanese seek, even calling for some punishment was significant for China, which usually opposes sanctions, particularly against an ally such as North Korea.

Pyongyang again demanded one-on-one talks with Washington and threatened to launch a nuclear-tipped missile if the U.S. doesn't help resolve the standoff. Bolton dismissed the demand, saying the North should instead "buy a ticket to Beijing," and rejoin stalled six-nation talks over its nuclear and missile programs.

The war of words suggested tough negotiations before the U.N. takes any action against North Korea. In the meantime, scientists and governments tried to determine what exactly happened early Monday, deep below the earth in North Korea's northeast mountains. The North Korean government has released few details.

A South Korean newspaper quoted a North Korean diplomat, whom it did not name, saying that the blast was "smaller in scale than expected.

"But the success in a small-scale (test) means a large-scale (test) is also possible," he said in comments posted on the Web site of the liberal newspaper Hankyoreh, which has good ties with the communist nation.

The diplomat also said the North could take "additional measures" and that it doesn't fear sanctions.

Philip Coyle, at the Center for Defense Information in Washington, a nongovernment think tank, expressed a growing view that "they got a partial result" and not the full-power explosion that they sought. Several Western estimates said the blast was less than a tenth the size of the 12-megaton bomb that the United States dropped on Hiroshima in 1945.

But "for them it was enough ... to say that it was a success. It helps them to claim that they are a nuclear power, and that the world should take them seriously, which is what they want. But I wouldn't be surprised if after several months they don't try again."

The White House said 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.

Democrats said the test was evidence of a failed Bush administration policy, which White House press secretary Tony Snow denied.

"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."

Sen. John McCain, R-Ariz., said President Clinton was to blame for his 1990s program to entice the North Koreans toward more cooperation. "The Koreans received millions and millions in energy assistance. They've diverted millions of dollars of food assistance to their military," he said.

After the reclusive regime announced it had set off an underground atomic explosion, the Security Council quickly condemned North Korea's decision to flout a U.N. appeal to cancel the test. The 15-nation council urged Pyongyang to return to stalled talks, refrain from further tests and keep its pledge to scrap its clandestine weapons program.

Diplomats said Tuesday there was a general agreement that the Security Council must pass a sanctions resolution in the next few days. The council's image suffered badly the last time it deadlocked over a major crisis, over the summer when it needed a month to pass a resolution on ending the war between Israel and Hezbollah.

"All I can say is that we are having a very good discussion, trying to identify what really we are going to be able to achieve, and i think there is general understanding also about the need to get our act together, and fast," Japan's U.N. Ambassador Kenzo Oshima said. "On that we agree."

Despite the positive assessment, familiar fault lines that have plagued past negotiations over North Korea already began to appear.

Japan, which holds the presidency of the Security Council for October, demanded the toughest sanctions of all, possibly including a blanket air and naval blockade of North Korea, as well as a ban on senior North Korean diplomats traveling abroad. In Tokyo, Japan's leader said the country could slap sanctions on North Korea without waiting for confirmation that it did indeed test a nuclear weapon.

Yet China, traditionally an opponent of Security Council sanctions, warned that the world must not focus too much on punishment. China can use its veto power in the council to block any move, and would likely have the support of Russia.

"Instead, the international community and the United Nations should take positive and appropriate measures that will help the process of de-nuclearization on the Korean peninsula," Foreign Ministry spokesman Liu Jianchao said.

One worry for Beijing is that too much pressure could cause economically unsteady North Korea to collapse, sending North Koreans streaming across the border into northeast China and inviting intervention by the American military.

Nonetheless, China was clearly rattled that the North went ahead with the test. Liu vented China's anger against its communist ally over the test for a second day.

"The nuclear test will undoubtedly exert a negative impact on our relations," Liu said. He said Monday's test was done "flagrantly, and in disregard of the international community's shared opposition."

The North warned that it would soon be able to put a nuclear warhead on one of its missiles.

"We hope the situation will be resolved before an unfortunate incident of us firing a nuclear missile comes," Yonhap, the South Korean news agency, quoted an unidentified North Korean official as saying. "That depends on how the U.S. will act." Yonhap did not say how or where it contacted the official, or why no name was given.

The news agency quoted the official as saying the nuclear test was "an expression of our intention to face the United States across the negotiating table."

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