The Arizona Republican demanded that the baseball league immediately crack down on performance-enhancing drugs after the disclosure this week that San Francisco Giants star Barry Bonds unknowingly took substances that may have contained steroids.
McCain said it was time baseball players and owners agree to a minimum standard for testing. "If not, clearly we have to act legislatively, which we don't want to do," he said.
Major League Baseball is facing one of the biggest crises in its long history, after Bonds was added this week to the growing list of top athletes linked to the BALCO steroid scandal.
New York Yankees Jason Giambi and Gary Sheffield, and former Olympic sprint champion Marion Jones were also among those named in a federal investigation into BALCO, a San Francisco area lab which officially focused on nutritional supplements and blood testing.
MLB commissioner Bud Selig has vowed to clean up the sport by imposing tighter controls and harsher penalties before the start of spring training.
Under an existing agreement, which runs through to 2006, a player who tests positive for the first time must undergo treatment and counselling.
A second offence results in a 15-day suspension without pay or a fine of up to $10,000 (£5,150). The penalties increase to 25 days or a $25,000 fine for a third positive test, 50 days or $50,000 for a fourth and one year or $100,000 for a fifth.
The penalties are less severe than in many other sports, where bans of at least two years are often imposed.
