SEOUL, South Korea - Secretary of State Condoleezza Rice said Thursday she will not presume to tell South Korea or China exactly how they should enforce U.N. sanctions on North Korea, but called on all nations to cooperate.
"I did not come to South Korea nor do I go anyplace else to try to dictate to governments what they ought to do," she said at a news conference.
She said the United States wants to lower tensions, not escalate them.
Rice's South Korean counterpart, Foreign Minister Ban Ki-moon, warned North Korea anew that it should do nothing to worsen tensions.
"A second nuclear test by North Korea should never take place," he said following meetings with Rice.
Rice is on an Asian tour in support of United Nations sanctions on North Korea for a nuclear test that rattled the world amid continued signs that North Korea may be preparing for a second nuclear test.
At the same time, she is reassuring Seoul that the United States stands behind its pledge to defend the country if the North attacked. She carried a similar message in Japan, her first stop on a four-day trip devoted almost entirely to crisis talks on the nuclear threat.
Acknowledging that different countries will take different approaches to enforcing the U.N. restrictions on North Korea, Rice said the United States wants to ensure that all nations cooperate.
She said initial reports that the U.N. sanctions would require a blockade or embargo on North Korean goods were exaggerated and that there is a model for action, citing an existing agreement among about 80 nations that is meant to counter the spread of nuclear materials or long-range missiles.
South Korea has not signed on to that 2003 agreement, the Proliferation Security Initiative, out of concern that it would provoke the North. Frustration over that position was one cause of tension between Washington and Seoul even before the nuclear test.
Rice described that existing program as "effective, but not confrontational."
"There are many ways to implement (U.N. sanctions) that have the same character," she said.
North Korea has a standing army of about 1.2 million, with millions more in reserve, and a supply of missiles capable of reaching Asian cities. North and South Korea technically are still at war more than 50 years after the Korean conflict ended.
The U.S. has 29,500 troops in South Korea, plus other air and naval forces in range. While the U.S. has no land-based nuclear weapons in Asia, it does have submarines equipped with nuclear weapons.
Rice's meeting with Ban was their first since his selection this month as the next U.N. secretary general. The two diplomats later were holding a rare three-way session with Japan's foreign minister, a sign that the Korean nuclear crisis has helped warm Japan's often frosty relationship with South Korea.
South Korea and China together account for two-thirds of overseas trade for the impoverished communist North, and South Korea hopes to one day reunite the two Koreas.
Meanwhile, a Chinese envoy delivered North Korean leader Kim Jong Il a personal message from China's president on Thursday in the highest-level Chinese visit to its isolated ally since the North's nuclear test last week.
Chinese Foreign Ministry spokesman Liu Jianchao said he had no details of the message conveyed by State Councilor Tang Jiaxuan in Pyongyang but said the visit was "very significant."
Tang, traveling as an envoy for President Hu Jintao, arrived in the North Korean capital on Wednesday.
Tang and Kim had "in-depth discussions on China-North Korea relations as well as the prevailing situation on the Korean Peninsula," Liu said at a regular news briefing in Beijing.
A U.S. official traveling with Rice said in advance that Tang was expected to carry a strong warning to the North not to conduct a second nuclear test. The North ignored previous warnings from China, its only ally, not to conduct the Oct. 9 underground nuclear test or to test-fire missiles over the summer.
Stung, China has adopted a tougher line against Pyongyang and signed on to the U.N. sanctions.
There were reports North Korea had told China it was ready to conduct up to three more nuclear tests. At the State Department in Washington, spokesman Tom Casey said, "We certainly haven't received any information from them, from the Chinese, that they've been told by Pyongyang that another test is imminent."
U.S. government officials, who spoke on condition of anonymity because of the sensitive situation, said there was no evidence to suggest a second test was imminent.
But given the underground nature of the testing, officials said, it could happen with little or no warning. Seoul has been reluctant to inflame the North as it pursues a policy of reconciliation that has led to unprecedented cooperation between the former wartime foes. In addition to hopes for peace, South Korea also fears an influx of refugees if the fragile government in Pyongyang were to collapse.
But the United States has expressed skepticism about some joint North-South projects, singling out a tourism venture run by South Korea at the North's Diamond Mountain.
The U.N. Security Council resolution passed last weekend calls on countries to inspect cargo on ships sailing to and from North Korea.
The South Korean news agency Yonhap said Seoul was considering whether to inspect all North Korean ships that stop in South Korean ports on their way to third countries.
Yonhap said the South won't give additional material or tools for projects to link rail lines and roads between the Koreas, which are separated by the world's most fortified border.
Seoul was also considering whether to ban future shipments of emergency aid promised after the North suffered devastating floods in mid-July, Yonhap said. Seoul already halted regular aid after the North test-launched a barrage of missiles in early July over international objections.
North Korea contends it needs nuclear weapons to counter U.S. aggression. The U.S. has said it does not intend to attack the North or topple its communist government.
In Tokyo, Rice said the United States is willing to use its full military might to defend Japan in light of North Korea's nuclear test. Japan is home to more than 35,000 U.S. troops
At her side, Japanese Foreign Minister Taro Aso drew a firm line against his nation developing a nuclear bomb.
In Washington on Wednesday, President Bush told ABC News that if the U.S. learned North Korea was about to transfer nuclear technology to others, the communist nation would face "a grave consequence." He did not elaborate.