For decades, U.S and China have recognized the importance of maintaining economic and political ties. But the relationship has not always been smooth. After this background report, the NewsHour historians and novelist Bette Bao Lord discuss the relationship between the two countries and President Clinton's upcoming visit to China.

KWAME HOLMAN: For the last 50 years, relations between mainland China and the United States have been a roller coaster ride. The Communist takeover of China in 1949 shocked the United States and resulted in a deep freeze in relations that would endure for more than 20 years. In American politics, rivals traded charges and accusations over who lost China.

The United States refused to recognize the Communist government in Beijing and helped keep China out of the United Nations. Instead, the U.S. dealt only with the losers of the Chinese civil war, the government of Chiang Kai Shek, which fled to the island of Taiwan. The freeze between the U.S. and the mainland deepened in the Korean War, as China sent troops to aid North Korea, while soldiers from the United States and other members of the United Nations fought for South Korea. China also sent supplies--but no troops--to North Vietnam in a war that cost more than 50,000 U.S. lives.

The first thaw in the relationship between the two global giants came in 1972 when Richard Nixon became the first American president to visit China while in office. He called the historic trip "the week that would change the world." It was a first step in the normalization of relations between the United States and China. The president shook hands with China's legendary leader, Mao Tse-Tung and accepted a gift of two giant pandas. At the Great Wall, Mr. Nixon said, "We don't want walls of any kind between peoples." On President Gerald Ford's 1975 trip, no new agreements were reached but the visit gave Mr. Ford the chance to meet the next generation of leaders who soon would succeed Mao. The relationship took another positive turn in December 1978.

JIMMY CARTER: The United States of America and the People's Republic of China have agreed to recognize each other and to establish diplomatic relations as of January 1, 1979.

KWAME HOLMAN: Though Mr. Carter never traveled to China while in office, a few weeks after formal relations were restored, he hosted Premier Deng Xiaoping during his nine-day trip to the U.S. Deng participated in talks at the White House and took a trip to a Texas rodeo. The two leaders agreed to upgrade their diplomatic representation and exchange ambassadors.

Ronald Reagan was greeted with a 21-gun salute in Tiananmen Square in 1984. His visit, which took him to the Great Hall of the People and the Great Wall, resulted in formal agreements, furthering scientific and cultural exchanges and greater cooperation on the development of nuclear energy projects.

On his February 1989 presidential visit, George Bush was presented with a bicycle. It was a reminder of how he got around Beijing when he served there as one of the first American diplomats during the Nixon and Ford administrations. Mr. Bush emphasized economic reforms, including more opportunities for trade. He too went to Tiananmen Square and during the visit, praised China's greater acceptance of human rights. Just four months later, Tiananmen Square took on a completely different symbolism for Americans and the rest of world when hundreds of democracy demonstrators were killed by the Chinese army. President Bush cut off all high level official exchanges between the two nations but sent a secret delegation to Beijing to persuade the Chinese to open their society. That mission was criticized by presidential candidate Bill Clinton.

BILL CLINTON: I believe the president erred when he secretly rushed envoys to resume cordial relations with China barely a month after the massacre in Tiananmen Square. The administration continues to coddle China, despite its continuing crackdown on democratic reforms.

KWAME HOLMAN: Since taking office, Mr. Clinton has pushed for what he calls a policy of engagement with China. Last year, he hosted Chinese President Jiang Zemin on his state visit to the United States. Today, members of Congress urged the president to press the Chinese leadership on the issue of human rights.

REP. SUE MYRICK (R-NC): We're here today to call upon the president to push for freedom and democracy in China. Mr. President, we wholly agree that China is of enormous economic and strategic importance to the United States. A constructive dialogue with China is in our nation's best interest. But any dialogue with China must include a frank discussion of human rights.

KWAME HOLMAN: Tomorrow, Mr. Clinton departs for his own state visit to China, which will include a welcoming ceremony in Tiananmen Square.