Barthez has missed the start of the season with a hip problem, which he picked up during a pre-season friendly in the Netherlands.

Ferguson was hopeful he would be fit for United's Champions League qualifier against Zalaegerszeg of Hungary this week.

The French keeper has resumed training, but Ferguson is still unsure how long Barthez will be out for.

"It's a delicate injury to the hip joint," Ferguson said. "He has been doing his gym work and taking part in training sessions as an outfield player.

"But we're not asking him to dive yet, the risk is too great. He won't be fit for Tuesday.

"If we qualify for the Champions League then we have three days to do something about it, depending on how he is."

Ferguson will have to act quickly if he is to sign a new keeper before next Saturday's deadline.

He has recently been linked with a move for Juventus stopper Fabian Carini and Brazil's World Cup-winning keeper Marcos.

Uruguay international Carini looked to be on his way to Arsenal, but the move broke down over personal terms.

Derby's Mart Poom, who almost joined United last year, and Tottenham's Neil Sullivan have also been mentioned as possible targets.

United have been looking for goalkeeping cover since Raimond van der Gouw, Paul Rachubka and Nick Culkin moved on in the summer.

Meanwhile, Ferguson and chief executive Peter Kenyon are due in Paris on Monday for talks with Rennes full-back Julien Escude.

It is hoped the latest round of negotiations will result in a transfer being concluded.