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 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 an audience.

Xi, 56, was due to meet Akihito at the imperial palace on Tuesday.

In his hour-long meeting with Japanese Prime Minister Yukio Hatoyama after his arrival, Xi thanked Tokyo for "making meticulous arrangements" for his visit.

"I want to further promote development of the strategic, reciprocally beneficial relationship between the two countries during my visit," he said as the media was allowed to cover the first few minutes of the meeting.

Hatoyama, whose centre-left government took power in September with a promise to seek closer ties with China and Japan's other Asian neighbours, said he welcomed the visit of a "next-generation leader."

Hatoyama, 62, told Xi Japan regards its alliance with the United States as the "cornerstone" of its diplomacy but that it is also "very important" to improve its ties with China, according to a foreign ministry press release.

"Japan, the United States and China are in a plus-sum relationship," he said.

Xi, noting that Tokyo-Beijing ties occupy a "very important place" in China's foreign policy, expressed his support for Hatoyama's proposal for an East Asian community, according to the statement.

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."

Hatoyama defended himself, saying the meeting "has major meaning for further progress in Japan-China relations. I don't think my decision was wrong."

Under Japan's post-war constitution, Akihito and other members of the world's oldest monarchy serve a largely ceremonial function and are barred from engagement in political activities.

Many Asian countries still hold bitter memories of the past aggression of Japan under Akihito's father, the late Emperor Hirohito.

The exceptional move to allow Xi's meeting with the emperor caused a stir in the Japanese media.

Some newspapers said Japan may have returned a favour for China's special treatment of a delegation of more than 600 led by the ruling party's powerful secretary general, Ichiro Ozawa, who was allowed to meet Hu last week.

Hatoyama's Democratic Party of Japan (DPJ) has pledged stronger ties with Asia and proposed a future East Asian Community with a single currency, along the lines of the European Union.

The premier has also pledged that he and his cabinet will stay away from Tokyo's controversial Yasukuni war shrine, seen by many other Asian nations as a symbol of Japan's past militarism, after visits there by previous conservative premiers badly harmed Tokyo-Beijing ties.

After his three-day visit to Japan, Xi will fly to South Korea, Myanmar and Cambodia before returning to China on December 22, officials said.

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