Two congressional leaders said Friday that the NFL Players Association may be using “using stall tactics” to avoid beginning blood-testing of players for human growth hormone.

Rep. Darrell Issa (R-Calif.), chairman of the House committee on oversight and government reform, and Rep. Elijah Cummings (D-Md.), the committee’s ranking Democrat, wrote that the union is demonstrating “a lack of urgency” to begin the testing program. Their letter was sent to NFL Commissioner Roger Goodell and DeMaurice Smith, executive director of the players union.

Issa and Cummings wrote that they “will be in touch with you shortly,” perhaps to schedule a follow-up meeting with the two sides about the HGH blood-testing program.

“At the end of our last meeting, the parties were put on notice that absent tangible signs of progress within two weeks, we would need to reconvene the parties,” Issa and Cummings wrote. “That deadline is near. Unfortunately, it appears that the players’ union may be using stall tactics to avoid complying with the collective bargaining agreement.”

The letter was sent two weeks after representatives of the league and union met with Issa and Cummings on Capitol Hill. The two congressmen announced after the meeting that blood would be drawn from players soon while the NFL and union continued to work out the details of a testing program.

Under an NFL plan, that blood would have been stored without being immediately tested for HGH. But the union said that it was not prepared to have blood drawn from players until the two sides reached an agreement on details of the testing program.

Union officials have said they have not received the information about the test they have been seeking.

Issa and Cummings wrote that the union declined an invitation last week from the U.S. Anti-Doping Agency to tour its facility and “be walked through every stage of the test.”

The league and union agreed to the HGH testing in the 10-year labor deal they completed in August. They targeted the opening of the season in early September to begin the testing.

The NFL would be the first professional sports league in the U.S. to blood-test its players for HGH with the consent of their union.

Three Democratic members of another House committee, the committee on energy and commerce, have urged its chairman to hold hearings on the issue.