He was due to sing in Tosca when he came down with flu

His Manchester MEN Arena show on 9 June has now been postponed and no replacement date has been fixed.

But fans are to be offered refunds or the chance to see him at Birmingham's NEC in October.

Pavarotti is set to appear alongside fellow tenors Placido Domingo and Jose Carreras in Yokohama on 27 June - between the World Cup semi-finals and the final.

It will be the fourth of the Three Tenors concerts, which began at the Italia '90 competition, for which Puccini's Nessun Dorma was the official theme.

Speculation

A spokeswoman for the Italian singer said: "Mr Pavarotti has been forced to change his schedule in order to accommodate the preparations and rehearsals for this concert.

"Discussions between the Manchester venue and management are taking place to determine a future date, which will be announced in the near future."

He is already scaling back performances

But the cancellation is bound to lead to further speculation about the career longevity of the singer, who is 66 years old.

After his withdrawal from a performance of Tosca last Sunday, Pavarotti indicated he had thought about retiring.

He cancelled his appearance the Metropolitan Opera at the last minute, saying he was suffering from flu.

Subsequently he told Italian newspaper Corriere della Sera that he might be forced to make the decision to retire soon.

"It's the most difficult decision, because I don't know yet if the moment has come or if the crisis of the past few days is down to health problems," he said.