SHANGHAI - Citing "overwhelming" evidence that North Korea sank a South Korean warship, U.S. Secretary of State Hillary Rodham Clinton warned the communist state Friday of international consequences.

After discussions in Tokyo, Clinton planned to consult with counterparts in Beijing and Seoul on appropriate measures to take after an international investigative team on Thursday blamed North Korea for firing a torpedo that sank the South Korean ship in March, killing 46 sailors.

"This will not be and cannot be business as usual. There must be an international - not just a regional, but an international - response," she told a press conference in Tokyo, flanked by Japanese Foreign Minister Katsuya Okada. The subject has come to dominate her three-nation tour through Japan, China and South Korea.

The Chinese have the most leverage over the reclusive regime, and Beijing's support for any international response to Pyongyang will be critical to its success. But China, North Korea's main ally and a veto-wielding permanent member of the Security Council, has thus far remained neutral.

While it was "premature" to discuss exact options or actions that will be taken, Clinton said it was "important to send a clear message to North Korea that provocative actions have consequences."

U.S. officials have refused to call the North's attack on the ship an act of war or state-sponsored terror, warning that an overreaction could cause the Korean peninsula to "explode." Instead, they said they would explore diplomatic steps through the U.N. or increase Washington's unilateral sanctions against North Korea's Soviet-style state.

Economic dialogue with China was supposed to be the main thrust of Clinton's Asia trip, but with Thursday's report blaming Pyongyang for sinking the Cheonan, her main task in Beijing will now be to try to persuade China to support U.N. Security Council action against North Korea.

In Shanghai, where Clinton traveled after her brief visit to Tokyo, two senior U.S. officials said she would try to persuade the Chinese to "acknowledge the reality" of what happened and support measures that would help persuade North Korea to change its behavior. The officials spoke on condition of anonymity due to the delicacy of the diplomacy.

Investigators from the five-nation team said a detailed analysis of the wreckage, as well as fragments recovered from the waters where the ship went down, point to North Korean involvement. Clinton described the examination as "thorough" and "scientific."

"The evidence is overwhelming and condemning. The torpedo that sunk the Cheonan ... was fired by a North Korean submarine," Clinton said.

North Korea denies it was responsible and has threatened to retaliate against any attempt to punish it with "all-out war."

North Korea "will regard the present situation as the phase of a war and handle all problems in inter-Korean relations accordingly," Ri Chung Bok, deputy director of the Secretariat of the Committee for the Peaceful Reunification of Korea, said in an exclusive interview with broadcaster APTN in Pyongyang.

Later, a spokesman for North Korea's Foreign Ministry denounced the U.S. for "absurdly" blaming Pyongyang.

"It is the intention of the present U.S. administration to suffocate (North Korea) politically and economically" with sanctions, he said, according to the state-run Korean Central News Agency.

Meanwhile, in Seoul, South Korean President Lee Myung-bak convened an emergency national security meeting, where he said the country was caught in a "perfect military ambush" but called for a cautious response to the sinking.