Her visit comes at one of the most sensitive times in U.S.-China relations, stepping into the middle of a controversy over how China and the United States can live together in the post-Cold War era.
"It is an extremely delicate phase in our two countries' relations," a leading Chinese expert on the United States said. "Mrs. Clinton's visit shows that the United States is trying to repair damage. How her visit proceeds will be watched closely by China's leadership."
Officially, Mrs. Clinton's trip is for no purpose other than to participate in the United Nation's Fourth World Conference on Women, a gathering of more than 4,750 delegates from 184 countries that officially opened yesterday. The participants' goal is to agree on a 120-page document designed to improve the status of women through specific actions that U.N. members will agree to take.
"A revolution has begun," said Gertrude Mongella, secretary-general of the conference. "There can be no spectators, no sideliners, no abstainers, for this is a crucial social agenda which affects all humanity."
Among the issues of contention to be discussed are abortion and the universality of human rights, which some countries believe are luxuries for rich nations. Small groups of experts will start debating the arcane points of language today while politicians and personalities, such as Mrs. Clinton, will deliver speeches.
The first lady also will travel to Huairou, the town 30 miles north of Beijing where 23,000 activists from private groups have met for the past five days. They have complained bitterly about surveillance and freedom of speech restrictions imposed by Chinese security personnel.
In the only incident in Beijing yesterday, Chinese security men barred Winnie Mandela from the welcoming ceremony, getting into a shoving match with her delegation members as they tried to enter the Great Hall of the People, China's legislative building and conference site.
Mrs. Mandela, the estranged wife of South African President Nelson Mandela who heads the African National Congress Women's League, said her bus had lost its way.
Members of the U.S. delegation, of which Mrs. Clinton is honorary chairwoman, say Mrs. Clinton will not specifically talk about China -- either to help improve relations or to criticize its human rights record.
"Mrs. Clinton is coming to address the conference on women. It happens to be in China. It could have been someplace else," Donna E. Shalala, the secretary of health and human services, said yesterday.
Mrs. Clinton will mention human rights, but in the context of the women's conference and not to specifically criticize China's human rights violations, said Rep. Constance A. Morella, a Maryland Republican.
"She will speak strongly about human rights and the implications will be there," said Ms. Morella, who is co-chair of a congressional delegation to the women's conference.
But that may not be good enough for many others, who are counting on Mrs. Clinton to make at least a reference to the host country's human rights violations.
Rep. Christopher H. Smith, a Republican from New Jersey, said yesterday that China's use of abortions, some of them forced, to control its population made it imperative that Mrs. Clinton issue a strong statement.
"To attend a women's rights conference in Beijing without commenting on this would be like attending a human rights conference in South Africa 10 years ago without making a country-specific condemnation of apartheid," said Mr. Smith, who co-chairs the congressional delegation.
Human rights groups also called on Mrs. Clinton to make a statement, especially after China's security police videotaped and reportedly roughed up members of a parallel conference. The other conference, a more informal gathering of representatives from non-governmental organizations, or NGOs, is U.N.-sanctioned and supposed to enjoy U.N. standards of freedom of speech and assembly.
"You cannot talk about advanced rights, such as equality in the workplace, when basic rights aren't secured, such as freedom of speech or protection against arbitrary arrest," said Robin Munro of Human Rights Watch/Asia. Mr. Munro's group, as well as Amnesty International, have urged Mrs. Clinton to at least condemn the harassment of the NGOs.
With the NGO meeting winding down and attention focusing on Mrs. Clinton and the official U.N. conference, a big protest is now unlikely, even though Chinese security forces continue to monitor the groups in violation of U.N. rules.
To show her sympathy with the non-governmental groups, Mrs. Clinton is expected to pay them a visit tomorrow. Senior administration officials say they fear that when she does, she might be confronted with an obvious human rights violation and would feel pressured into criticizing China.
"That is our worst-case scenario," a senior official said. "It would look once again like we are leading the charge against China."
Such a situation would set back weeks of delicate negotiations to repair frayed Sino-U.S. ties.
Relations sank to a six-year low after the leader of China's archrival, Taiwan, visited the United States earlier this summer. Later, human rights activist Harry Wu, a U.S. citizen, was arrested when he tried to enter China, raising calls for Mrs. Clinton to boycott the U.N. women's conference in retaliation.
Mrs. Clinton, however, was reportedly eager to attend the conference, and hours after Mr. Wu was released from custody and expelled from China, she agreed to attend.
Administration officials said there was no linkage between the two acts, but Rep. Doug Bereuter, who spent two days last week meeting high-ranking Chinese officials, said China sees it differently.
"They view her visit as an important affirmation of their hosting the women's conference," said Mr. Bereuter, a Nebraska Republican. "They view this as an extremely important step in our bilateral relations."
The U.S. delegation's reluctance to rock the boat was made plain Sunday afternoon after a Canadian woman at the NGO forum was videotaped and roughed up after distributing material critical of China's rule over Tibet.
Canada asked the United States to join it in an official "demarche," or diplomatic representation, to the Chinese government over the woman's treatment. U.S. officials refused, suggesting that the matter be referred to the United Nations.
On paper, at least, Mrs. Clinton will also take pains to avoid angering China. She plans no meetings with ordinary Chinese or Chinese dissidents. Her first speech, scheduled for noon today local time, is on "women and health security." She may draw on her experience as head of the Clinton administration's failed effort to reform the health care system.