Pakistan completed tests on 13 of its 15-man squad and five reserves this week but Akhtar and Asif have yet to feature, raising media speculation they might skip the event starting on March 13.
"Pakistan Cricket Board (PCB) chairman Naseem Ashraf has a zero tolerance on the use of banned substances so any member of the team going for the World Cup has to pass the screening, the in-house dope testing," PCB director operations Salim Altaf told AFP.
"The chairman has directed that nobody can go on the tour if this screening is not done."
Akhtar was banned for two years and Asif for one year in November after they tested positive for the steroid nandrolone.
But the new-ball pair's bans were controversially overturned by a PCB appellate committee in December, on the grounds they did not take the banned substance knowingly.
Experts have warned that Akhtar and Asif may still have banned substances in their systems after testing positive last year and face life bans if they test positive again.
Altaf brushed aside speculation over the dope tests on Akhtar and Asif.
"Everybody will feature otherwise nobody can go and that is the instruction of the chairman and we hope all speculations die down after this," said Altaf, a former fast bowler.
He also rejected suggestions the PCB was risking life bans for the pair if they test positive for a second time.
"If they failed tests which took place in September 2006 and this is now February 2007, the process is the same for everybody," he said.
Akhtar said he still hopes to be fit for World Cup despite battling to recover from knee and hamstring problems.
"I am going for another reassessment of my knee and hamstring injury in England later this week and only after that I am able to know about my chances of playing in the World Cup," Akhtar told AFP.
Asked when he was due to appear for testing, Akhtar refused to comment and said his first priority was to get over his injury.
"Right now I want my injury to heal and only after that I am going to think about anything else," said the 31-year-old.
Asif meanwhile also had an assessment in England last week after a recurrence of an elbow injury before returning home on Wednesday.
"Both Akhtar and Asif are consulting the specialist over their injuries and once these problems are overcome they will feature in the tests," said Altaf.
Another paceman Umar Gul, also included in the 15-man squad, is recovering from an ankle injury sustained on Pakistan's tour of South Africa last month.
Altaf said all the squad members will have to pass fitness tests as well.
"Before the departure of the team to the Caribbean all 15 players are going to subjected to a fitness test by a medical panel of the PCB," said Altaf.
Pakistan has until March 2 to replace any injured player in their squad. After the deadline only the International Cricket Council's technical committee is entitled to allow a injury replacement.
Pakistan also has ICC permission to replace any player who tests positive.
The Pakistan squad was due to start a World Cup tune-up camp in Lahore from Friday.