Six months before the Summer Games, American athletes are starting to worry. Athens just doesn't seem safe from afar, despite the most expensive security plan ever devised for an Olympics.

Among the most nervous are athletes who might be the biggest targets for terrorists -- NBA stars on the U.S. basketball team.

"The players are definitely concerned," said Jermaine O'Neal of the Indiana Pacers. "It definitely sits on your mind. If you wanted to send a message to the world, what better place is there to do it?"

Basketball players and other athletes told the Associated Press they are especially worried because the games will be held close to the Middle East in a country with a strong undercurrent of anti-American sentiment.

They're also not sure the $750 million plan to protect athletes will be enough. The cost is three times what was spent on the 2000 Sydney Games.

"There will be bomb-sniffing dogs and shady characters. You just hope they do everything they can," Seattle Sonics guard Ray Allen said. "From the American side, there's only so much we can do as far as security. They have to take care of their part before we get there."

Allen said he is also concerned about plans to house the Dream Team on the Queen Mary 2 in an Athens harbor.

"The only thing I can think of is the battleship that got blown up," Allen said, referring to the USS Cole, which was bombed in Yemen in 2000. "They came up on the side in a little boat."

U.S. security officials say they have confidence in the security plan, but they admit there are no guarantees everyone will be safe.

The plan was recently revamped, mostly because of American, British and French concerns about the possibility of snipers in the hills around Athens.

The November terrorist bombings in neighboring Turkey made preparations even more urgent. The blasts killed 63 people and injured more than 700.

It's hard not to look at those bombings as a wakeup call," said Bruce Hoffman, a terrorism expert at RAND, a think tank that often does work for the Pentagon. "It's just one step removed from Greece and those bombings showed a degree of planning and sophistication that is unsettling."

Athletes are already unsettled enough.

"The one thing is you don't want to live in fear, but also you are not on your home land," New Jersey Nets guard Jason Kidd said. "Knowing we are going to be one of the big stories there, you always have to be prepared and understand what's at stake."

Basketball players aren't the only ones worried about competing at the first Summer Olympics since the Sept. 11, 2001, terrorist attacks.

"It freaks me out a bit," said Hazel Clark, a member of the 2000 U.S. track team. "You just have to have faith God will protect us."

Already, would-be Olympians are being told not to wear team clothing or anything else that might identify them as Americans when not competing. Many say they don't plan to venture far outside the Olympic Village or U.S. training center in Athens.

The U.S. athletes will get added protection from a special security team assembled through the State Department. Security agents will probably accompany any groups of Americans outside the athletes' village, in the foothills on the outskirts of Athens.

After a slow start, Greek organizers -- with help from the United States and other countries -- are implementing a plan that includes 50,000 police and troops to guard Olympic venues and athletes.

Specialists from Russia, the United States, Britain and other countries are involved, and NATO troops will be on alert ready to enter the country if needed.

Security officials have held training exercises to prepare for chemical, biological or "dirty bomb" radioactive attacks, and the lone U.S. military base in Greece is storing emergency and medical equipment in case of an attack.

Some athletes say they try to ignore signs of possible trouble, while others say they can't. In December, anarchist groups claimed responsibility for firebomb attacks that damaged the home of an Athens judge and destroyed a car with U.S. license plates.

"I worry about it a lot," said Sean Townsend, 2001 national champion gymnast. "But I have full trust in our U.S. security team. I just try not to think about it because our main job is gymnastics."

After initial hesitation, the Greeks have warmed up to outside help. In November, FBI Director Robert Mueller went to Athens to warn organizers of holes in the security plan involving possible snipers and chemical or biological attacks.

Next month, U.S. forces will take part in an anti-terrorist exercise in Greece that will last 20 days.

Still, International Olympic Committee president Jacques Rogge acknowledged last month that there are no certainties.

"We are very satisfied," Rogge said. "But, of course, no one can guarantee 100 percent security."

That's what worries some Dream Team members, who will be the most visible of all U.S. athletes in Greece for the games, Aug. 13-29.

"Hopefully, things will be smooth and we'll get in there and play the games and get out of there, because death is permanent," O'Neal said.

USA Basketball executive director Jim Tooley said no players have said anything to him about being worried. Tooley noted that the safety plan for the team was put together with help from U.S. Olympic Committee security officials, NBA security forces and the FBI and CIA.

"We're comfortable with where we stand today with the information we have," Tooley said. "If we weren't comfortable we would certainly make alternate arrangements."

Still, Kidd says he's praying for a safe Olympics.

"I hope they are doing something. I mean, you just hope they don't leave any rocks unturned and that they use all their resources," he said.