WASHINGTON — Accusing the NFL players' union of "trying to back out" of an August 2011 agreement to start checking for human growth hormone, a congressman worried aloud Wednesday that the league will head into next season without a test for the banned drug.

"Hopefully as we move down the line, players will see how incredibly ridiculous it looks for them not to ... straighten this thing out," said Rep. Elijah Cummings of Maryland, the House Oversight and Government Reform Committee's ranking Democrat. "We're now getting ready to go into a third season, and it does not look very good."

The panel held a hearing to examine the science behind the testing, and heard from experts that it is reliable.

"No test is perfect ... but there hasn't been a single false positive," U.S. Anti-Doping Agency Chief Science Officer Larry Bowers testified.

While the latest, 10-year labor contract paved the way for HGH testing in professional football once certain parameters were set, the NFL Players Association wants a new study before it will agree to the validity of a test used by Olympic sports and Major League Baseball. The sides haven't been able to agree on a scientist to help resolve that impasse.

HGH is a banned substance that is hard to detect and used by athletes for what are believed to be a variety of benefits, whether real or only perceived — such as increasing speed or improving vision. Among the health problems connected to HGH are diabetes, cardiac dysfunction and arthritis.

"They say they need more time ... before doing what they agreed to do. To me, it seems obvious the Players Association is simply running out the clock," Cummings said. "Although they agreed to HGH testing, they are now trying to back out of the contract."