Chinese President Hu Jintao starts to pay a state visit to the United States from Tuesday to Friday, and the following is a brief introduction to the major exchanges of visits by leaders of the two countries.

Feb. 21-28, 1972 -- U.S. President Richard Nixon paid a visit to China, the first visit by a U.S president since the founding of the People's Republic of China in 1949. A China-U.S. joint communique, known as the Shanghai Communique, was issued in Shanghai on Feb. 28.

Dec. 1-5, 1975 -- U.S. President Gerald Ford visited China.

Jan. 28-Feb. 5, 1979 -- Chinese Vice-Premier Deng Xiaoping paid an official visit to the United States. On Jan. 31, agreements on cooperation in science, technology and culture were signed between the two countries.

April 26-May 1, 1984 -- U.S. President Ronald Reagan paid a state visit to China, during which the two countries signed four agreements on avoiding double-taxation and tax evasion and initialed an agreement on cooperation in the peaceful use of nuclear energy.

July 22-31, 1985 -- Chinese President Li Xiannian paid a state visit to the United States, the first by a Chinese president since the founding of the People's Republic of China. On July 23, the two countries signed four agreements and protocols, including one on the peaceful use of nuclear energy.

Feb. 25-26, 1989 -- U.S. President George Bush paid a working visit to China.

Oct. 26-Nov. 3, 1997 -- Chinese President Jiang Zemin paid a state visit to the United States. The two sides issued a China-U.S. joint communique, vowing to boost cooperation and work for a 21st century-oriented constructive strategic partnership.

June 25 - July 3, 1998 -- U.S. President Bill Clinton paid a state visit to China. During the visit, Jiang and Clinton held talks and the two sides issued three joint statements on South Asia, the protocol to the Biological Weapons Convention and the issue of anti-personnel mines respectively. During the talks, Clinton reiterated that the United States upholds the one-China policy, abides by the principles enshrined in the three Sino-U.S. joint communiques, and does not support independence for Taiwan, or "one China, one Taiwan", or "two Chinas", or its membership in any international bodies whose members are sovereign states.

Feb. 21-22, 2002, U.S. President George W. Bush paid a working visit to China. During his visit, Jiang Zemin and Bush held talks and the two leaders agreed that China and the U.S., both bearing significant influence on the world, should strengthen dialogues and cooperation and properly address their differences in order to push forward the Sino-U.S. constructive cooperative relations.

Oct. 22-25, 2002, Chinese President Jiang Zemin paid a working visit to the United States. Jiang and Bush exchanged views on important issues of common concern. The two leaders believed that China and the U.S., with broad and important common interests, should expand exchanges and cooperation in trade, culture and education, and boost dialogues and coordination on major regional and international issues to constantly push forward their constructive cooperative relations.