Liverpool start their league campaign four days later at promoted Sheffield United, with Kewell not expected to be able to train properly until the following week.

The Reds have revealed the 27-year-old is suffering from a problem known as septic arthritis, a bacterial infection in the joints of his left foot.

He is currently in hospital having had surgery to alleviate the injury, which was initially reported to be gout.

Kewell was seen on crutches limping to the dug-out ahead of Australia’s eventual World Cup exit at the hands of finalists Italy two weeks ago.

Now, following treatment this week, Liverpool have issued a statement explaining the problem.

A club spokesman said: “It is unfortunate that another Australian player spoke publicly about his condition rather than an official spokesperson for the national team.

“His team-mate suggested that Harry had been suffering from gout, which we can confirm was an incorrect diagnosis.

“Following Harry’s return to Liverpool and examination by our own medical staff, it became apparent he was suffering from an entirely different condition.

“This was identified as a septic arthritis; a bacterial infection in the joints of his left foot.

“Harry is currently undergoing treatment in hospital following a surgical procedure. He is expected to make a complete recovery and should be able to resume training in approximately six weeks’ time.”

Kewell’s international colleague Scott Chipperfield was quoted as saying “Harry’s got gout on his foot” following the 1-0 last 16 defeat by Italy.

The length of time Kewell will be sidelined will do nothing to help him maintain his first-team spot at Anfield, with Chile winger Mark Gonzalez now having been given a work permit and likely to be boss Rafael Benitez’s first choice on the left flank.

Brazilian acquisition Fabio Aurelio is able to play left-back and left-wing, adding a further obstacle upon Kewell’s eventual return.

Benitez is delighted with his free transfer signing from Valencia, saying: “Aurelio is a left full-back or a left-winger with a lot of quality.

“He can cross the ball superbly and he is maybe a better passer of the ball than Xabi Alonso.

“People will say ‘oh really?’ But you will see the quality of his crosses and passes with his left foot. He is also fantastic at set pieces.”

Gonzalez will also have plenty of time to cement his place in the side ahead of Kewell’s return, which my increase speculation Kewell’s days on Merseyside are numbered.

But Kewell said: “I have got to see what happens with my fitness in the immediate future, and try to get everything right. I am not thinking about anything except getting myself fit.”

Liverpool have confirmed another friendly, agreeing to visit Lincoln for a on August 16, four days before the Premiership season starts.

The match is part of the deal that took teenager Jack Hobbs to Anfield last season, when the defender played a major part in the club’s FA Youth Cup success.

But Liverpool have made it clear the side fielded at Sincil Bank – under the stewardship of new reserve boss Gary Ablett – will not be a strong one.

The match clashes with a string of international fixtures that week, which will rule out the Reds’ England contingent who should be involved in the match with Greece.

Also away on international duty will be Spanish trio Luis Garcia, Xabi Alonso and Jose Reina, while Craig Bellamy, Steve Finnan, John Arne Riise and Danny Agger are all expected to be playing for their countries.