BEIJING (AP) -- Let the party begin. The Beijing Olympics are just a year away.

Sprawling Tiananmen Square is the center of celebrations Wednesday for thousands of ordinary Chinese and hundreds of Olympic officials as countdown clocks across Beijing reach the one-year mark.

The magic moment is to come at 8:08 p.m. -- and 8 seconds -- marking one year until next year's opening ceremony on Aug. 8, 2008.

Eight is a lucky number in China, and everything seems on schedule for Beijing to host the most awaited and most expensive Olympics in history. Beijing's new anthem -- the just-released pop song "We're Ready" -- was to be part of a grandiose two-hour ceremony played out on a temporary stage built under banks of searchlights.

"From what we have seen so far, the preparations for Beijing 2008 are truly impressive in every regard," said International Olympic Committee President Jacques Rogge, who is in Beijing this week meeting students, planting trees and greeting Olympic sponsors.

"I don't think we have ever seen preparations on this scale."

China's Communist government has been efficient in building venues. Except for the iconic "Bird's Nest" National Stadium, all of the 37 venues are to be finished by the end of this year. Venue construction has eaten up only a part of the US$40 billion (euro30 billion) being spent on new subway lines and skyscrapers to remake the capital.

There have been few delays, and the US$2.1 billion (euro1.5 billion) operating budget has been offset by the vast revenue expected from TV and sponsorship. That has allowed attention to focus on Beijing's choking pollution, campaigns to "civilize" the city and the risks involved for China's authoritarian government.

Normally cautious with his words, Rogge warned hours before Wednesday's big party that some events next year could be postponed if the air is too dirty.

"Yes, this is an option," Rogge told CNN in a brief interview. "It would not be necessary for all sports, sports with short durations would not be a problem. But definitely the endurance sports like the cycling race where you have to compete for six hours, these are examples of competitions that might be postponed or delayed to another day."

Despite billions spent to move refineries and steel mills out of town, Beijing has been blanketed for weeks by choking industrial smog, limiting visibility to a few hundred meters (yards).

To guarantee clean air during the 17-day Olympics, about 1 million of the city 3.3 million vehicles are expected to be kept off the roads. Officials are also hoping to control the weather. Meteorologists began tests last month, firing rockets to disperse rain clouds -- a move to guarantee sunshine. They've also fired rockets to induce rain to clean the air.

"They've told us the factories will be closed for three months in 2008 and that they will have a directive to encourage residents to stay off the roads with their cars," said Steven Roush, chief of sport performance for the U.S. Olympic Committee.

Like other national Olympics bodies, the USOC is monitoring the quality of Beijing's air, laden with ozone, dust and exhaust from some aging vehicles.

Image is important with 550,000 foreign visitors and about 22,000 accredited media set to attend. In addition, up to 10,000 non-accredited journalists are expected.

Old habits like spitting, jumping ahead in line and littering are under siege in various campaigns aimed at improving behavior. From taxi drivers to 560,000 volunteers, everyone is being pressured to learn some English.

Chinese officials are also warning citizens to be good sports.

"It is natural for the Chinese people to hope and wish for good performances since China is the host country," said Wang Wei, an executive vice president of the Beijing organizing committee. "I also want to tell the Chinese spectators that while we can be a winner, we should also be a polite loser."

The hubbub is driving up hotel prices, which could increase 10 times. At the same time, the Communist Party wants charm, a soft edge to China's aggressive economy and recent scandals over food and product safety.

Revenue from local sponsorship is expected to be at least double that of Sydney or Athens with billions more spent on advertising and promotional campaigns.

Although many athletes will eat specialized diets provided by their own teams, Olympic organizers have also promised to track food electronically from the field to the consumer. The state-run China Daily newspaper reported recently that mice will be used to test food samples.

The biggest security threat may come -- not from al-Qaida -- but from protesters hoping to highlight causes like labor rights or China's role in the Darfur crisis. Other protests may center on Tibetans who seek autonomy, or Taiwan activists who want formal independence for the island.

"Great achievement is always accompanied by great challenges," said Jiang Xiaoyu, an organizing committee executive vice president. "While the Beijing Olympics are a great opportunity, we are also confronted with huge challenges."

The government earlier this year removed reporting restrictions and promised foreign journalists "complete freedom to report." However, some are still unhappy.

The Committee to Protect Journalists on Tuesday urged Beijing to free 29 imprisoned journalists and loosen restrictions on local reporters. It also called on the IOC to pressure China to increase press freedoms. On Monday, police detained journalists at a rare protest in Beijing.

"The Olympic movement is very pleased the focus is going to be on China in the lead up to the games ... in every way including human rights," said John Coates, an IOC member and president of the Australian Olympic Committee.

"We hope there will be change, we hope there will be improvements, but at the end of the day we are not a government and we are not the United Nations."

Rogge has called the games a "force for good." But Beijing-born Xu Xin, a political scientist at Cornell University, says the view is simplistic.

"The government has to strike a delicate balance between openness and control," Xu said. "Maintaining stability remains the primary concern whereas promoting openness and reform are secondary."

"In contrast with the conspicuous transformation of landscape and infrastructure in Beijing, any major political reform cannot be expected simply because of the Beijing Olympics."