“Should Sen. Mitchell uncover material suggesting that the scope of this investigation needs to be broader, he has my permission to expand the investigation and to follow the evidence wherever it may lead,” Selig said.

DuPuy said baseball considered Mitchell’s potential conflicts of interest.

“Given Sen. Mitchell’s integrity, given his background, he was absolutely considered to be the perfect choice for this job,” he said.

DuPuy said baseball had the power to force players to cooperate.

“My hope is that others will see it as we do, that it’s in the best interests of baseball and the individuals to be forthcoming, but I can’t predict,” Mitchell said.

However, Bonds does not plan to cooperate with the investigation, the New York Daily News reported.

New York Yankees first baseman Jason Giambi, who like Bonds testified before a federal grand jury in 2003, said he’d have “no problems” an inquiry. Giambi reportedly admitted to the grand jury that he had used steroids.

“I did the things I needed to do, took care of it and played last year and have just gone forward. I’m not really worried about it,” he said.

Teammate Gary Sheffield also testified and said of his cooperation: “If I have to, I will. I’m going to do whatever the law expects me to do, but other than that it’s a waste of my time.”

In a 1980 case involving pitcher Ferguson Jenkins, arbitrator Ray Goetz curtailed the commissioner’s power to order cooperation.

“Arbitrators have been reluctant to allow compelled, potentially self-incriminating testimony,” Selig said. “The investigatory authority of Major League Baseball, therefore, is particularly limited when the allegations relate to conduct that can create or has created a risk of criminal prosecution for the player.”

Selig would not address possible discipline that could result from the investigation,

“When this investigation is over ... that will be the time for me to make those kind of judgments,” he said.

Bonds enters the season with 708 homers, trailing only Babe Ruth (714) and Hank Aaron (755) on the career list.

“I assume physical constraints notwithstanding, Bonds will play the whole year,” DuPuy said.

Selig would not discuss whether baseball would commemorate Bonds’ pursuit of the home-run record.

“We’ll work those out in the coming weeks,” he said.

Slide show   Week in Sports Pictures Flying on the hardwood, racing on the rink, getting physical on the gridiron, and much more. more photos

Earlier Thursday, Victor Conte — founder of the Bay Area Laboratory Co-Operative — was released from a California prison. He spent four months there after pleading guilty to orchestrating an illegal steroids distribution scheme that allegedly involved many high-profile athletes.

Asked whether he gave Bonds steroids, Conte said: “No, I did not.”

“I plan to provide evidence in the near future to prove that much of what is written in the book is untrue,” Conte told the AP. He declined to list specific inaccuracies or what evidence he would provide, but said, “It’s about the character assassination of Barry Bonds and myself.”

Union head Donald Fehr and chief operating officer Gene Orza did not respond to e-mails seeking comment.

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