Major League Baseball and the players' union have agreed to expand their drug program to include random in-season blood testing for human growth hormone and a new test for testosterone, they said on Thursday.

The advanced testing will start this season, in what will be the sternest doping program in major North American professional sports.

"This agreement addresses critical drug issues and symbolizes Major League Baseball's continued vigilance against synthetic human growth hormone, testosterone and other performance-enhancing substances," MLB commissioner Bud Selig said in a statement.

The new steps moved baseball well ahead of the National Football League, which does not test for HGH or have a similar test for testosterone.

The US Anti-Doping Agency challenged the NFL Players' Association to follow suit in agreeing to such tests.

"This is a strong statement by the players and the league, not only confirming the scientific validity of the HGH blood test and the benefit of longitudinal testing, but also the importance of clean athletes' rights and the integrity of the game," TheUSADA said.

"This agreement, following the recent Congressional hearings on testing in the NFL, leaves no reason for the NFLPA not to step up and implement the same to give its players an equal level of protection and confidence that they deserve a level, drug-free playing field in the NFL."

Michael Weiner, executive director of the MLB Players' Association, said Major League players supported the expanded program.

"Players want a program that is tough, scientifically accurate, backed by the latest proven scientific methods, and fair," said Weiner. "I believe these changes firmly support the players' desires while protecting their legal rights."

The announcement came one day after the players' union criticized results of the balloting for the Baseball Hall of Fame, in which no one received enough votes for enshrinement in what appeared to be a referendum on widespread doping during what has become known as the game's 'Steroids Era'.

All-time home-run king Barry Bonds and seven-time Cy Young winning pitcher Roger Clemens, have playing records that would have ordinarily made them certain Hall of Famers.