BEIJING - Vice President Dick Cheney is taking praise to China for its efforts to prod North Korea to give up its nuclear ambitions, but U.S. officials cautioned against expecting a breakthrough.

Cheney arrived today in Beijing, the second stop on his weeklong tour of Asia, amid rising tensions over violence in Iraq.

All three nations on Cheney's itinerary have had civilians taken as hostages in Iraq, although those from South Korea and China have been released. The fate of three Japanese civilians remained uncertain Monday as Cheney wrapped up his three-day visit to Japan.

While relations between the United States and China have improved as the two nations worked together to resolve the North Korean nuclear impasse, differences remain over Taiwan, Hong Kong and human rights.

The Bush administration has been increasingly critical of China for trying to restrict moves toward democracy by Hong Kong, a former British colony now considered a special administrative region of China.

Taiwan and the rising tide of democratic sentiment there also remains contentious within U.S.-Chinese relations.

Ahead of Cheney's arrival, China urged the United States to stop adhering to a law that encourages Washington to sell defensive weapons to Taiwan.

By remaining committed to the Taiwan Relations Act, the United States is sending the "wrong message to Taiwan independence forces," Chinese Foreign Ministry spokesman Kong Quan told the official Xinhua News Agency. He said the act meddles in China's affairs and infringes its sovereignty.

Under the Taiwan Relations Act, the United States is pledged to defend the island off southeastern China if it is attacked from the mainland.

U.S. officials have expressed misgivings, however, about apparent moves on an independence-minded agenda by Taiwan's freshly re-elected president, Chen Shui-bian.

Cheney was to meet today with China's vice president, Zeng Qinghong. The vice president was scheduled to talk Wednesday with Jiang Zemin, former president and still the Communist Party chairman, and Jiang's successor as president, Hu Jintao.

Cheney ended his Japan stay with a visit to Emperor Akihito and other members of the imperial family and with a speech on the 150th anniversary of a U.S.-Japanese peace agreement, a document honored except for the large exception of World War II.

Cheney said the U.S. relationship with Japan was "one of the greatest achievements of modern history."

In words reflecting Bush's appeal for U.S allies to stand fast on Iraq and not bow to demands of insurgents and kidnappers, Cheney said, "The unity of America, Japan and like-minded nations saw us through the dark days of the Cold War, and with the same unity we will overcome the trials of today."