"Akhtar's injury is not very serious as an MRI scan has shown swelling and no fracture on the ankle but doctors have advised him not to train hard for a week," Pakistan Cricket Board director Abbas Zaidi told AFP on Wednesday.
"Akhtar's fitness will be re-evaluated next week," he said.
"Akhtar has bowled without any trouble since his twin knee operations in February this year and we hope that he recovers in time to spearhead the team's attack."
The top Pakistani paceman has not played active cricket since his team's third Test against India in January this year and is racing the clock to prove his fitness for Pakistan's tour of England starting next month.
Pakistan selectors are due to announce the final 16-man squad on June 9.
Pakistan will play four Tests followed by five one-day matches. The first Test starts at Lord's on July 13.
The 30-year-old Akhtar, who has been plagued by series of injuries during his eight-year career, had vowed to play his part in the series against England.
"I can't wait more to play my part in England. It is always fun to play in England and since both the teams have good bowling attacks I see the series as a great challenge," Akhtar had said.
Some 21 players of a preliminary squad are currently attending Pakistan's conditioning camp in Lahore under coach Bob Woolmer.