Speaking at a tennis tournament in Florida, Ms Williams, one of America’s top sports stars, was giving voice to the unease among US athletes about the threat of terrorism in Athens in August.

The Wimbledon singles champion, making a comeback from a knee injury, said: “I think my security and my safety and my life is a little bit more important than tennis, and so if it became a real concern to where I personally wouldn’t feel comfortable, then I wouldn’t go to Athens. Because I like my life. I like to live, like waking up in the morning.”

Robert Mueller, the Director of the FBI who has visited Greece to discuss security, gave warning last week that there was the risk of an al- Qaeda strike at the Games.

A recent poll found that 52 per cent of Americans believe an attack is likely at the Games and 37 per cent believe that American athletes are the most likely target.

“We don’t know of any specific security threats against the US team or the Games,” Jim Scherr, chief executive of the US Olympic Committee, said. “However, it is obvious the world has changed and there are security concerns. And at the end of the day we know there’s no such thing as a 100 per cent safe environment.”

The US Olympic Committee has vehemently denied that the 575-strong US team has any plan to boycott the event because of security concerns.

But under pressure from Washington extraordinary security arrangements are being put in place to help to safeguard the Games. Nato has agreed to provide Awacs reconnaissance aircraft and a naval force; a Czech biological warfare detection battalion will be on standby.

Greece, which plans to deploy more than 50,000 soldiers and police, recently mounted a two-week counter-terrorism exercise involving 400 US special forces to prepare for possible bombings, hijackings and biological attacks.

Jose Rodriguez, the CIA’s counter-terrorism chief, and Vice-Admiral Henry Ulrich, the commander of US naval forces in the Mediterranean, visited Athens during the exercise, as did David Venness, Britain’s top counter-terrorism official.

Fears about the Athens Games have been heightened by the bombings of synagogues and British targets in nearby Istanbul late last year and the recent attacks on commuter trains in Madrid.

A number of American athletes have publicly expressed disquiet in recent weeks about the dangers of terrorism at the first Summer Games since the September 11, 2001, attacks.

Ms Williams said she was “really excited” about working with her sister Venus to retain the Olympics doubles gold they won in Sydney in 2000, where Venus Williams also took the singles title. But she said security “is definitely a concern of mine”.

She added: “I agree you can’t stop living your life because you are scared something is going to happen. I’ve got to be able to keep moving. I’m that kind of person.

“At the same time I’m very aware of things that are going on in the world. I read a lot so I’m very aware of a lot of stuff. It’s very unfortunate but it’s just either you go or you don’t go, and hopefully I will go.”

Other high-profile American sports stars to voice their worries include the basketball “Dream Team”.

“The players are definitely concerned,” Jermaine O’Neal, of the Indiana Pacers, said. “It definitely sits on your mind. If you wanted to send a message to the world, what better place is there to do it?” Ray Allen, of the Seattle Sonics, said that in the light of the 1998 attack on the USS Cole in Yemen he was anxious about plans to accommodate the Dream Team aboard the Queen Mary 2 in a harbour in Athens. “The only thing I can think of is the battleship that got blown up,” he said. “They came up on the side in a little boat.”

Hazel Clark, a member of the 2000 US track team, said: “It freaks me out a bit. You just have to have faith God will protect us.”

Stacy Dragila, the pole vault gold medal winner in Sydney, said: “I have to realise that people do hate Americans. That’s unfortunate. You just want to limit the distractions or the possibilities of creating a problem.”

However, the swimming star Nathalie Coughlin spoke for many Americans when she said she refused to worry about security at the Games. “It’s not something I can do anything about physically, other than worry about it, and what does that achieve?” she said. “It’s one of my biggest dreams to go to the Olympics. The threat of terrorism is looming whether I’m in the States or in Athens.”

Dain Blanton, who won gold in beach volleyball in Sydney, said: “It’s definitely in a part of the world that causes some concern but I believe that the people they have working on security are the best in the business and, as an athlete, you’ve got to move ahead and do what you do. You can’t be too concerned if an incident happens or not.”

US safety officials have offered athletes safety tips such as not wearing US colours when not competing. Many athletes say that they do not plan to venture far outside the Olympic Village.

Explore World News

• World Agenda

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Afghanistan News

• Asia News

• Africa News

• Ireland News

Times Recommends

• No apology for Germany’s own Nazi victims
• Intricate web of fear and hope tying down deal
• Victims remembered a year after Mumbai attacks