Amir, 30, played two County Championship games for Gloucestershire earlier this season when Naseem was injured and will make his T20 debut for the club against Somerset on Friday night, subject to PCB clearance.

Naseem, the 19-year-old fast bowler, returned to Pakistan earlier this month when his father fell ill and while his condition has improved, he will not return to Bristol due to "a hastily arranged Pakistan Cricket Board training camp," according to Gloucestershire.

Naseem played only four games in his time at Gloucestershire due to a shoulder injury which he suffered on debut. "He has shown incredible dedication and work ethic, despite some small issues meaning he couldn't take the field as much as he and we would have liked," Steve Snell, Gloucestershire's performance director, said.

"It has been great to see him develop as a young man - his English has improved immensely, which is something he should be very proud of. He is a very popular member of the squad, and we very much hope to see him back playing in Bristol in the years to come.

"We're delighted to welcome Mohammad back to the squad. He's a proven international performer and to have his experience available to us for the remainder of the Blast tournament will be invaluable."