MELBOURNE, Australia — Depending on which tennis player you ask, the new drug-testing regime for top international athletes is either too intrusive or a necessary evil.

The main issue of the system, which became effective in tennis on Jan. 1 after being adopted by the International Tennis Federation at the Beijing Olympics, is a provision requiring players to say where they are going to be for an hour each day, every day.

That doesn't mean they will be tested every time. But if officials show up to conduct a test and the player isn't there, it's one strike. Three strikes is considered a doping violation.

The 28 Summer Olympic sports federations accepted the code before the 2004 Athens Games, but not all have fully complied with the rules. Compliance is required for inclusion at the Olympics.

The ITF manages the program on behalf of the Grand Slams and the ATP and WTA Tours.

A number of cyclists, soccer players and volleyballers are pursuing legal action in Belgium, calling the code an invasion of their privacy. Top-ranked tennis player Rafael Nadal has said he plans to join in. Spanish journalists quoted him as calling the system a "disgrace" and "intolerable," saying many players believe they are being treated like criminals.

But second-ranked Roger Federer and Serena and Venus Williams say that while they may not like it, it's critical to tennis' integrity to prove that its athletes are clean.

"It's a tough system, no doubt," Federer said Saturday, a day before he will play Nadal in the Australian Open final. A win would pull him even with Pete Sampras' record of 14 Grand Slam titles. "It's a significant change to what we were used to before, so I think it takes some getting used to it."

He said doping seemed to have become so sophisticated that anything less stringent would leave cracks for offenders to slip through.

"I feel like this is how you're going to catch them, right?" Federer said. "You're not going to catch them ringing them up and saying, 'Look, I would like to test you maybe in two days.' The guy's cheating and they're smart, right?

"It's an hour a day. I know it's a pain, but I would like it to be a clean sport, and that's why I'm OK with it."

Integrity was also cited by the Williams sisters, who have 17 Grand Slam singles titles between them.

"We think that drug testing is good for sports," Venus Williams said. "That's really how we feel. Any details of that that may need to be worked out or that are a little bit confusing for the players, we continue to work on that as Player Council members."

Some players have already run into problems. Mike Bryan, who teamed with twin brother Bob to win the Australian Open doubles title Saturday, has two strikes after what he called innocent mistakes. One would come off in mid-April; another missed test in the meantime would likely result in a suspension.

"You got to communicate ... where you're going to be at all times," Mike Bryan said. "They even want to know when you're flying in, the day you arrive, if you're going to be at the hotel for an hour. We missed a couple. Just weren't thinking. Just down in L.A. One time I got a flat tire. You just got to be ready for anything."

"I think once someone gets banned for missing a few tests, then you hear the stories — and they're kind of ridiculous stories — then I think we'll probably have a problem with it," Bob Bryan said. "If it's one of our friends that goes out, if Mike gets banned ..."

Still, they agreed that in an era when failed drug tests in some sports seem to be in the news every day, something has to be done.

"It's fair across the board," Mike Bryan said. "You don't want doping in tennis. It's good. I think we just got to get used to the strictness."