"The bowlers have faced fitness problems and it hit the performance of the team. For the moment we have told them not to accept any contracts," Zakir Khan, director of cricket operations, told Reuters.
Gul, 24, had a contract offer from Gloucestershire while Asif, who missed the World Cup with an elbow injury, had previously played for Leicestershire.
Zakir said a decision on allowing other players to appear for English county sides had not been taken as yet.
Younis Khan is signed up to play for Yorkshire while leg-spinner Danish Kaneria is due to play for Essex.
"The board is in the process of finalising a comprehensive international and domestic programme after the World Cup. We want all our pacers fit and available," Zakir said.
Pakistan were knocked out of the World Cup in the first round after losing to West Indies and Ireland.