Members of the Senate were said to be hours away from imposing drug-testing and penalty requirements on all major league sports when the deal was reached.
The new programme will require baseball players to submit to several drug tests each year, during and between seasons, with lengthy suspensions for drug use. Repeat offenders can be banned for life.
US lawmakers said they would hold off on legislation for now, but called on other professional sports leagues to follow baseball's lead.
The agreement, which must be ratified by both the players and baseball owners, is similar to a proposal offered earlier this year by baseball commissioner Bud Selig.
