LONDON (Reuter) - World leaders Wednesday paid warm tribute to China's late paramount leader Deng Xiaoping for his role in opening up China economically and diplomatically and voiced hopes for a peaceful transition of power in Beijing.

But prominent dissidents called on China to release political prisoners and predicted a power struggle.

President Clinton called Deng, who died Wednesday, an "extraordinary figure on the world stage over the past two decades."

In a statement during a visit to Boston, Clinton expressed sadness at

Deng's death and described him as "the driving force behind China's decision to formalize relations with the United States" in the late 1970s.

Secretary of State Madeleine Albright, visiting London, paid tribute to Deng and told reporters: "It would obviously be a great advantage to the Chinese as well as to all of us if there were a smooth transition (in Beijing)."

Albright, who plans to consult with Chinese officials whether to continue with a planned stopover in Beijing next week, said Washington would particularly remember Deng for the important part he played in normalizing Sino-American ties.

But the 1989 Tiananmen Square killing of pro-democracy demonstrators was "very troublesome to everybody that has been following the issue of human rights in China," she said.

"But I think also one does have to see him as a historic figure who did in fact open China up... It is a mixed assessment," she added.

Former President George Bush praised Deng as a "remarkable leader" who brought benefits to millions of his countrymen by opening up China's economic system.

Bush, who was U.S. ambassador to China from 1974 to 1976 and met Deng in China shortly after becoming president in 1989, said he "played a critical role" in establishing strong bilateral ties.

Canadian Prime Minister Jean Chretien expressed regret but said feelings were mixed because of Deng's record on human rights.

Commenting on Deng's opening up China but also ordering tanks into Tiananmen Square, Chretien said: "There's always mixed feelings on that situation. That's why whenever we meet with the leaders of China we always mention the rule of law."

In Taiwan, Beijing's nationalist rival, a senior official urged people to treat Deng's death calmly, saying the government already has policies for the post-Deng era.

Taiwan media quoted a military spokesman as saying the armed forces were on alert for latest developments.

The Dalai Lama, Tibet's exiled spiritual leader, voiced regret Deng died without resolving questions over Tibet. Tibet was culturally separate, ruled by a Buddhist elite until 1950, when China's People's Liberation Army took over the area.

Japanese Prime Minister Ryutaro Hashimoto said he was greatly saddened by Deng's death, adding "the Japan-China relationship is of growing importance for peace and stability in Asia and the world."

Governor Chris Patten of Hong Kong, the British colony which will revert to Chinese sovereignty at midnight on June 30 after than 150 years of colonial rule, said Deng's "concept of 'one country, two systems' helped to... lay the foundation for Hong Kong's stability and prosperity after 1997."

In London, British Prime Minister John Major said Deng's "initiative played the crucial part in creating today's economically dynamic and successful China."

Major also praised his "visionary concept of one country, two systems" for guaranteeing that Hong Kong's capitalist system would stay in place for 50 years after reversion to Chinese rule.

French President Jacques Chirac hailed Deng as the main force behind his country's modernization and said he "will go down in history as the main architect of the transformations China underwent in the past 20 years."

Former Soviet president Mikhail Gorbachev, who like Deng rose through Communist Party ranks to spearhead changes as revolutionary as Deng's said: "The fate of this man was very close to me."

U.N. Secretary-General Kofi Annan expressed "deep sorrow" and called Deng a key architect of modernization and economic development.

But Xiao Qiang, the leader of Human Rights in China, a prominent New York-based rights group, called on China to free all political prisoners to give the Beijing government "a good start" after Deng's death.

Chinese-American human rights activist Harry Wu, who spent 19 years in Chinese labor camps in the 1960s and 1970s and has since devoted himself to exposing alleged human rights abuses, predicted Deng's death would spark a power struggle.

"The empire system is always looking for No. 1. Who will become the next real emperor? That means a power struggle," Wu told Reuters in a telephone interview from his northern California home.