Athletes who test positive for steroids would be banned for a half-season instead of two years for a first offense under changes made Tuesday to gain support for steroid legislation in the Senate.

The bill, sponsored by Sens. Jim Bunning, R-Ky., and John McCain, R-Ariz., calls for a one-season ban for a second steroid offense and a lifetime ban for a third. It would apply to Major League Baseball, the NFL, NBA, NHL and baseball's minor leagues.

The leagues and their players' unions say they should continue to set their own drug-testing rules and penalties through collective bargaining.

"I think, seriously, that they are under the opinion that we will not act," said Bunning, a former major league pitcher. "We tried to explain to them that we are going to act because of their failure to do so, and I don't think it's sunk in."

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Senate Minority Leader Harry Reid, D-Nev., has signed on as a co-sponsor. He planned to meet with House leaders and sponsors of similar bills in that chamber.

Under current rules, a first failed drug test draws a 10-day ban in Major League Baseball (roughly 1/16th of a season), a 10-game ban in the NBA (about an eighth of a season), a four-game ban in the NFL (a quarter of a season), and a 20-game ban in the NHL (about a quarter of a season).

The previous Senate bill was based on the penalty model used by the Olympics — a two-year suspension for an athlete failing a steroids test for the first time and a lifetime ban for a second offense.

The House has several versions of the bill, including one by Rep. Cliff Stearns, R-Fla., that now closely mirrors the Senate measure.

"That we can agree on the penalties is very important," Stearns said in a telephone interview. "It's good news for trying to pass a steroid bill."

House Government Reform Committee Chairman Tom Davis, R-Va., whose panel held a March 17 hearing with baseball stars Rafael Palmeiro, Mark McGwire, Jose Canseco and others, has told Bunning and McCain that he probably would accept the three-tier penalty structure, Davis spokesman Dave Marin said.

During a series of congressional hearings and in private meetings with lawmakers, the commissioners of the pro leagues have criticized the earlier suggested penalties as too harsh.

Banning pro athletes for two years for a first offense would be "depriving them of their livelihood," NHL commissioner Gary Bettman said last week before a meeting with Davis. "The penalties should be severe, they should be harsh, but they shouldn't be such that the punishment doesn't fit the crime."

In April, baseball commissioner Bud Selig proposed raising that sport's penalties to a 50-game suspension for an initial positive test, a 100-game ban for second-time offenders and a lifetime ban for a third violation. Union head Donald Fehr rejected that proposal, and the sides have been negotiating.

The Senate bill would mandate that each player is tested at least five times a year and would urge leagues to erase records achieved with the help of performance-enhancing drugs.

The legislation would take effect a year after passage, giving the sports that time to change their own steroid policies and make them at least as tough as the law.