Visiting Chinese Vice Premier Wu Yi, right, shakes hands with Hiroshi Okuda, Chairman of Federation of Economic Organizations

Japan says it is at a loss as to why China's Vice Prime Minister Wu Yi at the last minute canceled a meeting Beijing had requested with Japanese Prime Minister Junichiro Koizumi.

The sudden cancellation of Monday's meeting between China's vice prime minister and the Japanese prime minister is being interpreted here as a diplomatic slap at Tokyo.

Japanese officials say they were told that "sudden duty" in China compelled Vice Prime Minister Wu Yi to quickly leave for Beijing on a chartered flight from Tokyo.

Prime Minister Koizumi told reporters he has no idea why China canceled the discussion, but he remains willing to meet with them at anytime.

Reporters asked Mr. Koizumi if his plans to again visit a Shinto shrine seen as a symbol of Japan's past militarism caused Ms. Wu to change her schedule.

Mr. Koizumi says he has no idea whether that might have been the case, but he stresses that he has not tried to exacerbate the already frayed relationship with China.

Japanese Foreign Ministry officials say Chinese diplomats made it clear that the change of plans had nothing to do with the controversial shrine, although some Japanese news media quote other officials here as contradicting that view.

Chinese President Hu Jintao on Sunday complained during a meeting with Japanese lawmakers in Beijing about Mr. Koizumi's plans to visit Yasukuni. Mr. Hu said that a visit would damage bilateral ties "in an instant."

China strongly opposes Japanese leaders paying their respects at Yasukuni because it honors convicted World War II criminals, along with all of Japan's war dead.

Ms. Wu arrived in Japan six days ago primarily to visit the China pavilion at an international exposition near Nagoya. She had been scheduled to return home on Tuesday after meeting with Prime Minister Koizumi.

In a speech earlier in the day in Tokyo, the Chinese vice prime minister gave no indication she would not meet with Mr. Koizumi. In her remarks, Ms. Wu said it was necessary to change the status of the current relationship, which she called "not satisfactory or benign," as quickly as possible.

Ms. Wu says that at a summit in Jakarta last month, the Chinese president proposed ways to improve and develop ties with Japan. She says this demonstrated the strong will of the Chinese leaders to promote cooperation between China and Japan, and that Japan responded positively to the proposal.

Sino-Japanese relations have ebbed to their lowest point in three decades. There were sometimes violent anti-Japanese protests in several Chinese cities last month. Demonstrators said they were angered by new Japanese history textbooks, which downplay early 20th century imperial Japanese atrocities in China and Korea. The demonstrators also said they opposed Japan's bid for a permanent seat on the United Nations Security Council.