BEIJING — With four days left before the start of the 2008 Summer Games, Chinese officials have not lived up to key promises they made to win the right to host the Olympics, including widening press freedoms, cleaning up their capital city's polluted air and respecting human rights.

The failures were evident today:

—A thick pall of smog covered Beijing, raising concerns that endurance events such as long-distance races would have to be moved out of the city. Some still held out hope that emergency measures would clear the city's air by Friday.

—Near Tiananmen Square in the heart of the city, police scuffled with protesters who said they were evicted from their homes to make way for Games-related development.

—Chinese censors continued to block access to politically sensitive Web sites for thousands of foreign journalists gathered at the Olympic press center.

These failures stand in contrast to the Herculean efforts China has made to prepare for the Olympics, building world-class venues, housing and other infrastructure.

Eager to impress a world audience, Chinese organizers have spent an estimated $40 billion on the 18-day event and built breathtaking facilities such as the landmark National Stadium, known as the Bird's Nest, where the opening ceremonies will be held Friday.

However, before and after 2001, when China won the right to host the Summer Games, Chinese Olympic officials repeatedly said they'd use the Games to improve the country's human rights record and allow reporters unfettered access to cover the competitions.

"We will give the media complete freedom to report when they come to China," Wang Wei, the secretary general of the Beijing Olympic Bid Committee, told a press conference in 2001. "We are confident that the games coming to China not only promote our economy, but also enhance all social conditions, including education, health and human rights."

When they applied to host the games, Beijing officials also had completed a Candidature File, in which they agreed to meet specific requirements. Although the International Olympic Committee said the file is a public document, Beijing Olympics officials didn't follow through Monday on a request by McClatchy to see the Candidature File they completed.

Reached by phone, the Beijing Olympic organizing committee's head of media operations, Sun Weijia, declined to comment.

A model file found on the International Olympic Committee Web site, however, requires host cities to provide athletes with a healthy physical environment, to give the news media open access and to honor the International Olympic Committee's charter, among other measures.

One of the charter's six fundamental principles states, "Any discrimination with regard to a country or a person on grounds of race, religion, politics, gender or otherwise is incompatible with belonging to the Olympic Movement."

Critics, including top U.S. officials, said Chinese officials have violated those agreements by tightening repression of political dissent in advance of the Games and not allowing reporters covering the Olympics full access.

Some critics look back and say that it was easy to believe most of the official statements.

"The argument certainly appeared plausible, if not compelling," recalled Rep. Christopher Smith, a New Jersey Republican, who visited Beijing last month. "But in the years, now months, run-up to the Olympics, the reality has been numbingly disappointing."

A recent report by the human rights advocacy group Amnesty International found that Chinese officials have stepped up their persecution of followers of the outlawed Falun Gong spiritual movement, and detained rural petitioners seeking redress on a range of political issues.

"I suppose it was just a bunch of words when they made those promises," said Sophie Richardson, the Asia advocacy director for the U.S.-based watchdog group Human Rights Watch. "When the Chinese government is serious about something, they do it."

In 2001, after China was awarded the games, Beijing Olympic officials signed a second document, called the Host City Contract, which includes legally binding requirements for hosting the Games. An International Olympic Committee spokeswoman said today that the contract isn't a public document, although previous Olympic host cities have released their contracts.

The criticisms have put Chinese officials on the defensive, and state-controlled media quoted Chinese Premier Wen Jiabao saying over the weekend, "China is a responsible country. We will fulfill the promises we made for the Olympics."

Despite making verbal pledges, Chinese officials likely didn't legally agree to take any action to improve the country's human rights record, said Susan Brownell, a U.S.-based adviser to the Beijing City Olympic Education Standing Office.

Brownell said she'd seen neither Beijing's Candidature File nor the Host City Contract but had talked to people who'd seen the contract.

"The idea's out there that China made commitments on human rights, but it's simply not true," Brownell said. "Nobody was in any mood to make any promises then."

Chinese officials, however, emphasized human rights and press freedoms in their Olympic bid after losing out to Sydney to host the 2000 Summer Games.

Suspecting that International Olympic Committee members were still wary of China following the 1989 Tiananmen Square massacre, officials made statements that International Olympic Committee members interpreted as pledges to relax the government's authoritarian grip on its citizens in the run-up to the games.

In January 2007, the Chinese government also significantly loosened restrictions on foreign media, which allowed reporters to travel freely across the country and interview anyone who consented. Those new provisions end on Oct. 17, 2008.

But a series of disasters this year have left China's leaders wary of social and political instability. Snowstorms socked in much of the nation in late January and early February, the worst ethnic riots in nearly two decades erupted in ethnic Tibetan areas of China and a 7.9-magnitude earthquake in Sichuan on May 12 took about 80,000 lives, by the most recent count.

While authorities offered journalists unprecedented access around the quake zone, large Tibetan-inhabited areas of western China remain blocked, in defiance of their promises.