Pope's aides admit he is unable to work normally

The Archbishop of Canterbury, Rowan Williams, has been told by the Pope's aides not to expect a substantive discussion with the ailing pontiff when he meets him at the Vatican today, according to two sources privy to preparations for the visit.

The warning is the first known admission from within the Pope's circle of advisers that his health problems have begun to limit his ability to carry out the essential functions of his office. Until now, aides had insisted that despite his evident frailty the Pope's mind was as sharp as ever, and he remained firmly in command of the Catholic church, taking all the important decisions and monitoring the crucial debates.

That is evidently no longer the case. It was not clear whether the latest, confidential advice from the Vatican meant the Pope was physically unable to sustain a prolonged conversation, or had undergone an erosion of his intellectual powers.

Rumours have been circulating in Rome for months that the 83-year-old Pope alternates between periods of lucidity and confusion. But last Sunday there was a first public indication that he could be losing his grip on events, when he announced the creation of a new batch of cardinals and got wrong the most crucial piece of information. He told the crowd in St Peter's Square that the ceremony was set for September, not October.

But last night Cardinal Karl Lehmann, head of Germany's Catholic Bishops Conference, said: "The Pope is weak and ill but he is still alive spiritually and mentally. He still has his responsibilities fully in hand."

This will be Dr Williams's first visit to Rome since he became primate of the Anglican church. He is being accompanied by the Catholic Archbishop of Westminster, Cormac Murphy-O'Connor. It is an indication of the warm relations between the two men at a time when their churches are as far as ever from unity.

The deep divisions of opinion between Anglicans and Catholics, especially over gay priests and the ordination of women, were thought to have been discussed by Dr Williams at meetings with Vatican officials yesterday.