Chinese President Hu Jintao lauded closer cooperation with Japan when he arrived for a state visit intended to nurture trust between the Asian powers despite rifts over energy resources and security.
Hu was greeted in Tokyo by senior Japanese officials and flag-waving, mostly Chinese well-wishers. Downtown, some 7,000 police were deployed ahead of threatened protests by hundreds of right-wing activists who see China as a danger.
But China is promoting itself as a friendly neighbour after years of feuding over Japan's handling of its wartime aggression, and Hu has stressed forward-looking goals for his five days of ceremony, speeches and deals, as well as table tennis and perhaps pandas.
China's second ever state visit to Japan comes as it seeks to calm international tensions over Tibetan unrest, which has threatened to mar Beijing's Olympic Games, a showcase of national pride.
With the two economies increasingly intertwined, Hu said better ties were important to both countries' prosperity.
"I sincerely hope for generations of friendship between the people of China and Japan," Hu wrote in a message to Japanese readers of a Chinese magazine, Xinhua news agency reported.
Cooperation has "brought real benefits to the people of both countries and spurred the growth and development of each," Hu said. "These achievements are worth treasuring by the people of China and Japan."
The Beijing Games were "Asia's Olympics and the world's Olympics," Hu added.
Certainly much is at stake in ties between Asia's two biggest economies. China replaced the United States as Japan's top trade partner last year, with two-way trade worth $236.6 billion, up 12 percent from 2006.
But while China's fast growth offers market opportunities, Beijing's accompanying expansion in diplomatic and military reach has stirred deeper anxieties in Japan -- over disputed energy resources, military power and the safety of Chinese exports.
Hu's efforts to court Japan could yet stumble on these rifts. "Although the iceberg between China and Japan has melted, fully warming relations require further efforts from both sides," a commentator wrote in China's People's Daily on Tuesday.
The political climax of Hu's visit is set to be a summit on Wednesday with Prime Minister Yasuo Fukuda, when they hope to unveil a joint blueprint for managing ties in coming years. But it was unclear whether the avowals of friendship would narrow rifts or merely bathe them in warm words.
Japanese media reports said touchy references in the document to Taiwan, human rights, and Japan's hopes for a permanent seat on the U.N. Security Council were still under negotiation.
A Japanese Foreign Ministry official said both governments had to deal with citizens wary of the other nation's intentions.
"The people's sentiment in both countries is still fragile, so we have to improve people's feeling through this visit," said the official, who spoke on condition of anonymity.
The two country's are quarrelling over the rights to gas beds beneath the East China Sea, while a row over Chinese-made dumplings laced with pesticide that made several people sick has become, analysts say, a symbol of Japanese alarm at China's rise.
Ping-Pong and Panda
Officials from both sides had earlier raised hopes of a breakthrough in the gas dispute before Hu's visit. Hu on Sunday told Japanese reporters that a plan acceptable to both sides was possible. But a swift compromise seems unlikely.
Japan also wants greater transparency about China's surging defence spending, set at 418 billion yuan ($60 billion) for 2008, up 17.6 percent on 2007 and outstripping Japan's defence budget. Foreign critics say China's real military budget is much higher.
Tokyo wants Chinese backing for a permanent seat on the United Nations Security Council, an issue that in 2005 fuelled anti-Japanese protests in China, where there is deep rancour over Japan's harsh 1931-1945 occupation of much of the country.
For its part, China has pressed Japan to spell out again its stance on Taiwan, the self-ruled island that Beijing says must accept reunification.
Tokyo has said it supports "one China" that includes Taiwan, which was a Japanese colony for much of the first half of the 20th century and retains close ties to Japan.
Still, the two sides are keen to stress forward-looking goodwill and are to issue a joint document on fighting climate change, a key topic for Japan as host of the July G8 summit.
Hu will give a speech to university students in Tokyo, he may play table tennis with Fukuda and he might also offer Japan a panda to replace one that died in a Tokyo zoo in April.