CHINESE President Jiang Zemin and Premier Li Peng yesterday conveyed messages of ''deep condolences'' to the family of China's ''old friend'', former United States President Richard Nixon, who died yesterday morning. The leaders praised Mr Nixon as an ''outstanding politician'' who, together with the late Chairman Mao Zedong and Premier Zhou Enlai, ''opened the door to Sino-US diplomatic relations'' in the early 1970s. After leaving office, Mr Nixon achieved considerable success in his endeavours to broaden and improve Sino-US relations, they said. The two leaders expressed the hope that both China and the US could continue to work together to further develop the bilateral relationship set in place by Mr Nixon 22 years ago. Although Mr Nixon visited China on seven occasions, he will be remembered here almost exclusively for his ground-breaking trip to Beijing in February 1972, which paved the way for the establishment of diplomatic relations between the United States and China after more than two decades of isolation and hostility. The visit was portrayed as a personal triumph for both President Nixon and his host Chairman Mao, but it was really their chief aides, Secretary of State Henry Kissinger and Premier Zhou, who did all the work before and during that historic eight-day visit. Mr Nixon and Chairman Mao did little more than exchange compliments and discuss poetry, not surprising since the chairman, then 78, had recently suffered a mild stroke and was incapable of holding a conversation for more than an hour or two. Mr Nixon spent most of his time at banquets and sightseeing, and attended a mind-numbing performance of one of Madame Mao's model operas. Meanwhile, Mr Kissinger and Premier Zhou hammered out the now famous ''Shanghai Communique'' which has formed the basis of Sino-US relations ever since. The former president was inordinately proud of the communique, describing it in his memoirs as a ''brilliant formula''. Although Mr Nixon, with characteristic immodesty, described his 1972 visit as ''the week that changed the world'', he was sensible enough to realise it was only a beginning. In his toast to Premier Zhou at the concluding banquet to the visit on February 27, Mr Nixon said the communique was ''not nearly as important as what we will do in the years ahead to build across 16,000 miles and 22 years of hostility which have divided us in the past''. Just two years later, Mr Nixon was out of the White House, forced to resign after allegations of criminal misconduct during the Watergate affair but he retained his fascination with China, visiting the Middle Kingdom on six further occasions in his role as elder statesman and ''old friend of China''. While most of these later visits were ceremonial, his controversial trip to Beijing in 1989, just four months after the June 4 massacre, proved to be one of the turning points in Sino-US relations. Mr Nixon did not shy away from private and public expressions of outrage over the deaths of hundreds of innocent civilians in Beijing, but he made it clear to his Chinese hosts, including paramount leader Deng Xiaoping, that China and the US still needed each other and that it was a matter of utmost importance that the two countries maintained a constructive relationship. Mr Nixon was well aware that such a mission of rapprochement would not be well-received in many circles in the US, but as he said in his memoirs: ''I believed that doing what I could to restore momentum to one of the most important bilateral relationships in the world was more than worth the risk to my own image. ''I knew the American people were realistic enough to understand that we had to continue to have constructive relations with the most populous nation in the world,'' he wrote. Upon his return to the United States, Mr Nixon immediately briefed President George Bush on his trip and once again stressed the need for constructive engagement. Mr Bush did not need much convincing having sent his national security adviser, Brent Scowcroft, on a top secret mission to Beijing in early July. One tangible result of Mr Nixon's visit was the release of dissident Fang Lizhi and his wife who had been holed up in the American Embassy in Beijing since the massacre. Mr Nixon suggested to Mr Deng that some ''small, symbolic steps'', such as allowing Mr Fang to leave the mainland, ''would give President Bush ammunition to fight long-time opponents of China and reassure those who want to be friends''. Mr Deng appeared amenable to the suggestion, saying there was a ''simple way out''. ''Fang Lizhi must give a written statement confessing his crimes and the US side must give assurances that he will not be allowed to carry out anti-Chinese Government activities abroad. After this, China can take some measures,'' the patriarch reportedly said. Mr Nixon followed up his initiative on April 3, 1990, with a letter to Mr Deng, and three months later an uncharacteristically silent Mr Fang was allowed out of the country, never to return. Throughout his more than two decades of ''constructive engagement'' with China, Mr Nixon was a firm believer in realpolitik, in not letting differences in ideology get in the way of the big geopolitical picture. On his final trip to Beijing in April last year, Mr Nixon told Premier Li that a ''good constructive relationship'' would benefit both countries, a sentiment wholeheartedly endorsed by Mr Li and Mr Jiang. Up to the arrival of Bill Clinton in the White House last year, it was the Nixon-Kissinger line which dominated US policy towards China. But after initially taking a tough stance on human rights abuses, President Clinton seems to be moving towards Mr Nixon's way of thinking. China's Most Favoured Nation trading status, the bedrock of the bilateral relationship, appears safe for another year and President Clinton is now actively considering separating it from the question of human rights altogether.