San Francisco ? Baseball commissioner Bud Selig expressed concern Saturday about fresh allegations that Barry Bonds used performance-enhancing drugs in 2003 and said they were further cause for a tougher policy on steroid use to avoid tarnishing the game.

Selig told reporters at the American League championship series game in Boston that a San Francisco Chronicle story based on a tape recording purportedly of Bonds’ trainer is “just a further manifestation of why we need a very strict steroid policy. Until we have one, we’ll have this kind of situation.”

The Chronicle obtained from an anonymous source a nine-minute recording it said was of Bonds trainer Greg Anderson, one of four people charged in a steroid scandal involving a Bay area nutritional supplements firm.

The speaker on the tape is heard saying Bonds used an “undetectable” performance-enhancing drug during the 2003 season and boasting that he would be tipped off up to two weeks before random drug testing, the newspaper said. Bonds has denied taking steroids.

“I’m concerned,” Selig said, cautioning that “these are merely allegations. I’m not ready to pass judgment.”

But he said the issue was detracting from the game.

“Here we are in Game 3 of the Red Sox-Yankees — people have waited for this all year — Cardinals and Houston, and what are we sitting here and talking about?” Selig said. “This is not good for the sport. This is not good for any of the parties involved, and, of course, I include the fans.”

The Chronicle quoted Anderson as saying he was confident Bonds could pass a drug test, not just because the drugs could be masked but because he would be warned in advance.

“I’ll know like probably a week in advance or two weeks in advance before they’re going to do it,” Anderson was recorded as saying, according to the Chronicle.

The league banned the use of steroids beginning with the 2003 season. The tape recording was made in the spring of that year, the Chronicle said.

Anderson, 38, a longtime friend of Bonds’, also said that he had experience using and dispensing performance-enhancing drugs that could escape detection, according to the report. He said the drug he was giving to Bonds also was given to Olympic athletes.