Seoul (AP) – Japan said Friday it is slapping new sanctions on North Korea by clamping down on money transfers, while the leaders of Japan and the U.S. pledged cooperation in taking the North before the U.N. Security Council over the sinking of a South Korean warship.

International pressure is mounting on North Korea over the sinking, which a multinational team of investigators blamed last week on a North Korean-made torpedo. Forty-six South Korean sailors died in the March 26 disaster, the worst military attack on the South since the Korean War.

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

Any Security Council action would need the backing of key permanent member China. South Korean President Lee Myung-bak was to lay out the case against North Korea in talks Friday with Chinese Prime Minister Wen Jiabao, a South Korean government official said on condition of anonymity in line with ministry policy.

Wen arrived in Seoul a day before a summit with the leaders of South Korea and Japan on the South Korean island of Jeju.

China, North Korea's main ally, has refrained from committing to Security Council action.

Senior U.S. officials said Wednesday that China had indicated it was prepared to hold the North accountable for the torpedo attack and could join in some kind of formal Security Council rebuke.

However, asked about Beijing's stance Thursday, Chinese Foreign Ministry spokesman Ma Zhaoxu simply called the issue "highly complicated" and said China's position remained unchanged.

"China does not have firsthand information. We are looking at the information from all sides in a prudent manner," Ma told a regularly scheduled news conference in Beijing.

Tensions have been rising daily on the Korean peninsula since the May 20 release of the investigation report.

South Korea slashed trade, resumed anti-North Korean propaganda broadcasts across the border and on Thursday launched large-scale naval exercises off the coast, with U.S.-South Korean drills to follow in the coming months.
North Korea threatened Thursday to attack any South Korean ships entering its waters and scrapped an accord meant to prevent naval clashes. Still, North Korea allowed South Korean workers to cross the border Friday for jobs at a joint industrial facility in the North.

Japan, which already bans trade with the North, said Friday it will reduce the amount of money that can be sent to North Korea without being reported to the Japanese government. Tokyo also said it will slash the amount of cash travelers can take into North Korea – an apparent bid to target funds funneled to the North by ethnic Koreans in Japan.

Calling the sinking of the ship "unforgivable," Chief Cabinet Secretary Hirofumi Hirano suggested in Tokyo that the government is considering additional sanctions.

Separately, Japanese Prime Minister Yukio Hatoyama and President Barack Obama jointly condemned the attack in a phone call and vowed to cooperate with South Korea on taking North Korea to the Security Council, the White House said.

"The president and the prime minister called on North Korea to end its provocative behavior toward its neighbors and to abide by its commitment to eliminate its nuclear-weapons program and to fulfill its other international obligations," the White House said in a statement.

(Associated Press writers Jean H. Lee in Seoul and Shino Yuasa in Tokyo contributed to this report.)