SEOGWIPO, South Korea — The premier of China, North Korea's main ally, offered condolences today to South Korea for the sinking of a warship blamed on North Korea after promising that Beijing — under pressure to punish the North — would not defend any country guilty of the attack.

Premier Wen Jiabao later joined the leaders of South Korea and Japan in a three-way summit on the southern Korean island of Jeju, saying he hoped it would help achieve peace.

"I hope this summit will conclude with solid results and that we will try together to ensure that it will contribute to world peace," Wen said, according to a Korean-language transcript released by the South Korean president's office.

A multinational team of investigators said last week that evidence proved a North Korean torpedo struck the ship, and South Korean President Lee Myung-bak has pledged to take the North to the U.N. Security Council.

North Korea has denied responsibility and warned that any retaliation or punishment would mean war.

The two-day summit was expected to be overshadowed by the sinking in March of the 1,200-ton Cheonan, which killed 46 sailors in one of South Korea's worst military disasters since the 1950-53 Korean War.

But the summit's first session today focused on improving economic cooperation. The ship sinking was not discussed but is on Sunday's agenda, said Kazuo Kodama, a Japanese Foreign Ministry spokesman.