China's Vice President Xi Jinping on Monday kicked off an Asia tour in Japan, where a row has broken out over a breach of protocol for his hastily arranged meeting with Emperor Akihito.
Xi, who is widely expected to succeed Hu Jintao as China's president in 2012, is on his first visit to Japan since he took office in March 2008.
The vice president was scheduled to meet Prime Minister Yukio Hatoyama, whose centre-left government took power in September with a promise to seek closer ties with China and Japan's other Asian neighbours.
Xi was due to meet Akihito at the imperial palace on Tuesday.
Hatoyama's government has drawn criticism for extending special treatment to Xi by allowing him to meet the emperor despite China having missed the usual deadline for requesting such a meeting.
The Imperial Household Agency normally demands that requests by foreign visitors to meet the emperor be filed at least one month in advance, but Xi's request for an audience was made on November 26.
Japan says the rule for such early notice was put in place because of concerns over the health of Akihito, 75, who underwent an operation for prostate cancer in 2002.
Former prime minister Shinzo Abe, still an influential figure in the opposition conservative Liberal Democratic Party, lashed out at Hatoyama's "political use of the emperor" after the government asked the palace last week to bend the usual rules and facilitate the meeting.
"I feel strong resentment," Abe told reporters. "It's not too late to ask the Chinese side to drop the plan."