Negotiators for the NFL and the players union will meet with anti-doping experts next week as they try to reach an agreement on HGH testing before the start of the season, people familiar with the negotiations told The Associated Press.

Though the league and union reached a general agreement in their new labor deal to test for human growth hormone, the union is waiting to see the specifics of the program before giving its final OK.

The union has asked the World Anti-Doping Agency for documentation about the accuracy of the seven-year-old HGH test.

People familiar with the negotiations, who did not want their names used because the talks were supposed to remain confidential, said the meeting with officials from WADA, the U.S. Anti-Doping Agency and other experts is set for next week, with the goal of answering all questions about the test.

The union, long skeptical about blood tests that must be used to detect HGH, wants to review the information before agreeing to any test. Officials from the NFL, which has pushed for HGH testing since 2008, said they were surprised at the union's reluctance to sign off on the testing. The HGH test has been available and widely accepted by scientists and Olympic sports organizations since 2004.

"To go through an entire two-year-plus period where there was no discussion concerning the accuracy of the test, then suddenly, to see discussions about the test and the science arise in the last 24 hours of negotiations, it does not seem to be based on concern for the facts," said Adolpho Birch, the NFL's senior vice president of law and labor policy.

NFLPA spokesman George Atallah did not return messages left by AP seeking comment.

As part of the collective-bargaining agreement signed earlier this month, the NFL Players Association and league confirmed "that the program on anabolic steroids and related substances will include both annual blood testing and random blood testing for human growth hormone."

But the union wanted to see the details before officially agreeing to anything, and they have not been worked out.

"We said we would agree to it when we were satisfied with the testing, the procedures, and more importantly, the reliability of the testing available," a person familiar with the union's stance told the AP. The person spoke on the condition of anonymity because of the sensitivity of the negotiations.

If no agreement on HGH testing is reached, the league would operate under its old policy, which did not test for HGH. Birch, in charge of the NFL's testing program, said that could take one of the union's top priorities — a third-party arbitration system to review positive tests and their subsequent penalties — off the table.

"Beyond that, there's little use in speculating," Birch said when asked what the NFL could do if the union doesn't agree to HGH testing.

Aware of the players' longstanding resistance to blood testing, the NFL was among the leagues who funneled money into research for a urine test that would detect HGH. Any such test, however, remains years away, so the league pushed for blood testing, saying it would be an important part of any new contract.

Anti-doping experts have long criticized the NFL and Major League Baseball for not testing for HGH. Baseball tests minor league players, and earlier this week, Rockies Triple-A player Mike Jacobs received a 50-game suspension after a positive test for HGH and became the first North American pro athlete to be punished for taking the drug.

"You have to question their motives why, especially in light of the recent positive in baseball, that they're retreating from wanting to put this in place," USADA CEO Travis Tygart said. "There doesn't seem to be any legitimate reason for all these questions when, over seven-plus years, top scientists in world in almost every testing agency have been using this test for deterrence and detection."