Shoaib (left) and Asif will not travel to the Caribbean with Pakistan

Shoaib has been unable to recover from a knee injury while Asif has been carrying a niggling elbow problem.

Yasir Arafat and Mohammad Sami will replace the pace duo and join the squad in the Caribbean before the World Cup opener against the hosts on 13 March.

"Their withdrawal has nothing to do with doping," Pakistan Cricket Board spokesman Pervez Mir insisted.

"They were due to feature in dope tests once they regained full fitness but for us the chapter is now closed.

"We did our best and waited because [captain] Inzamam[-ul-Haq] wanted them in the team as they are our best bowlers.

"But reports of their injuries were not good and we could not have waited any more."

Arafat is an all-rounder who bowls medium pace and has played just seven one-day internationals, while Sami is an experienced paceman.

"It is a big blow for us, but I am confident that Yasir Arafat and Mohammad Sami will live up to the expectations," team coach Bob Woolmer said.

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"They will join the team in a week's time and we hope to overcome our injury problems with a united team effort."

The squad flies out to the West Indies later on Thursday.

Shoaib and Asif both tested positive for nandrolone last September but had lengthy doping bans quashed on appeal in December after claiming they had not knowingly taken the banned substance.

The World Anti-Doping Agency is in turn contesting that appeal result in the Court of Arbitration for Sport

The PCB asked all its players to submit for drugs tests by 28 February.

Shoaib and Asif did not do so, raising unsubstantiated speculation that they still had traces of nandrolone in their system.