Mike Friedman, Bobby Lea, Sarah Hammer and Jennie Reed were among about 200 athletes from an American delegation of 596 who were issued masks by their national governing bodies to combat pollution in Beijing.

"They've now seen how their actions have been perceived," Scherr said. "They were very eager to take the right action, which was to apologize to their hosts."

U.S. Olympic officials released the statement from the foursome, who said the masks were not intended as anything but a precautionary measure.

"We offer our sincere apologies to BOCOG, the city of Beijing, and the people of China if our actions were in any way offensive. That was not our intent," the message read. "The wearing of protective masks upon our arrival into Beijing was strictly a precautionary measure we as athletes chose to take, and was in no way meant to serve as an environmental or political statement.

"We deeply regret the nature of our choices. Our decision was not intended to insult BOCOG or countless others who have put forth a tremendous amount of effort to improve the air quality in Beijing. We look forward to putting this incident behind us while we prepare for our competition next week."

U.S. officials said they would not prevent athletes from using masks to combat pollution, whether in sports events or not, if they felt it was needed because of air quality conditions.

"They have the right to wear masks if they feel it's in their best interest to do so," Scherr said. "Hopefully they won't have to use them and the air quality will be good."

The perception that Beijing's pollution, which prompted a shutdown of factories and reduction in auto travel during the Olympics, was so harmful that Olympians needed masks on arrival was seen as a slap in the face to organizers.

"You never want to go to somebody else's place and cause any embarrassment and in this case some of them did," said USOC chairman Peter Ueberroth, who said the cyclists apologized without prompting from U.S. Olympic officials.

"We're not chastising anybody. They came forward of their own volition."

U.S. cyclists wore the masks in the airport before even being exposed to the Beijing air over concerns that extra exposure to pollution might affect their breathing and therefore diminish their results in Olympic cycling events.

"It probably wasn't the most opportune time for these athletes to wear these masks," Scherr said. "They were overly cautious. Those athletes have written an apology to BOCOG."

Scherr noted that fractions of seconds can decide the fate of the competitors involved and that each was simply looking for every possible edge by wearing the masks as a precaution.

"It wasn't in the best judgment at the time," he said. "We believe, hopefully, this will be the last incident of this kind."

Steve Roush, the U.S. Olympic chief of sport performance, met with the cyclists regarding their using the respiratory masks, which have an air filter within them. Any U.S. governing body seeking masks were provided with them.

"It's not a very fancy device," Ueberroth said.

Roush also said air quality has improved every day in Beijing so far.

"The trend is the direction we wanted to see it go," he said. "Clearly it's a direction BOCOG and the IOC wanted to see."