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ttack, which killed 46 South Korean sailors in March, was part of a reckless pattern of aggression by North Korea, Gates charged Saturday.
"The question people have to contemplate is, what are the consequences for a North Korea of an unprovoked attack on a neighbor? For nothing to happen would be a very bad precedent here in Asia," Gates said, addressing an international security summit.
He did not mention China's financial and diplomatic support for North Korea but said "the nations of this region share the task of addressing these dangerous provocations."
The United States and South Korea want China to approve a new international condemnation or punishment of the North. South Korea took its case to the U.N. Security Council on Friday. China is one of five veto-holding members of the council.
China is the communist North's closest ally and largest patron, giving it economic and political pull over an otherwise reclusive and antagonistic regime. The United States and South Korea want China to use that clout to rein in the North Koreans.
In a tense exchange during the defense conference in Singapore, Gates dismissed suggestions by a Chinese general that Washington was being hypocritical in criticizing North Korea but not Israel for its commando raid on an aid flotilla in the Mediterranean Sea this week.
"There is a wide gap in the U.S. attitude and policy to the two instances," said Maj. Gen. Zhu Chenghu of China's National Defense University. He did not endorse the U.S.-backed international finding that the North sunk the warship Cheonan with a torpedo.
Gates said the attack on the warship was a surprise operation conducted "without any warning." Israel had issued several warnings to the flotilla not to enter its territorial waters, he said.
"I won't make judgment on responsibility or fault" in the Mediterranean incident, Gates said, adding that he favors an international investigation to determine responsibility.
"But I think there is no comparison whatsoever between what happened in the eastern Mediterranean and what happened to the Cheonan," he said.
He denied that the sinking revealed holes in the security the large U.S. military presence in Asia is supposed to provide for allies such as South Korea.
"What it demonstrates is that a surprise and unprovoked attack is very difficult to defend against," Gates said.
