The pair declined, when asked at a tribunal hearing their case, if they wanted their 'B' samples examined after their first ones tested positive for a banned drug, tribunal chief Shahid Hamid told reporters Friday.
The tribunal, which also includes former captain Intikhab Alam and doping expert Waqar Ahmed, is probing their case after they tested positive for banned performance enhancing steroid nandrolone.
The results prompted Pakistan to withdrew both from their Champions Trophy squad in India last week.
"Akhtar and Asif have accepted the results of the dope tests and when we offered them to have tests on their B samples they refused to have another test," Hamid said.
The pair earlier Friday gave statements to the tribunal which was appointed by the Pakistan Cricket Board to investigate the scandal.
The tribunal, which meets again Saturday, will make recommendations to the PCB and is expected to submit its findings in two weeks.
"We offered both the players to have retests on B samples which they declined, which implies that they are not questioning their failed dope tests," Hamid said.
"They had explained their point of view and we are now going to take medical opinion to examine the situation," said Hamid, who has summoned two doping experts for Saturday's hearing.
When asked whether the players have admitted taking banned drugs, Hamid refused to comment.
The panel also Friday recorded statements from PCB's chief medical officer Sohauil Saleem.
Asif came alone to the hearing and was questioned for over an hour while Akhtar was accompanied by doctor Nauman Niaz and stayed for the same duration, a PCB spokesman said.
During a preliminary hearing, which lasted around four hours last week, the tribunal handed medical reports to both the pacemen and asked them to record their statements in the next hearing.
Akhtar, who returned to cricket only last month after missing Pakistan's Test series in England with an ankle injury, has said he never cheated in cricket.
"I have not knowingly taken any performance enhancing drugs and would never cheat my teammates or opponents in this way," the 31-year-old Akhtar said.
Both Akhtar and Asif face a two-year ban, the minimum for a first offense under International Cricket Council doping rules. However, the PCB said it will take its own decision since the tests were conducted internally.