VATICAN CITY (Reuters) - The late Pope John Paul was wounded by a knife-wielding priest in 1982, a year after he was shot in St Peter’s Square, but the injury was kept secret, his former top aide says in a documentary film.

Cardinal Stanislaw Dziwisz also discloses that when John Paul was unable to pronounce words several days before his death in 2005, he told his aides that if he could not speak any more the time had come for him to die.

Dziwisz, who is now cardinal of Krakow, Poland, was John Paul’s private secretary and closest aide for nearly 40 years, including all of his 27 years as pontiff.

The documentary, called “Testimony” and narrated by British actor Michael York, is a film version of a memoir published by Dziwisz last year but with some additions.

It will make its official premiere at the Vatican on Thursday night in the presence of Pope Benedict.

On May 12, 1982, the pope was visiting the shrine city of Fatima in Portugal to give thanks for surviving a first assassination attempt a year earlier on May 13, 1981, when he was shot in St Peter’s Square by Turkish gunman Mehmet Ali Agca.

A crazed ultra-conservative Spanish priest, Juan Fernandez Krohn, lunged at the pope with a dagger and was knocked to the ground by police and arrested. The fact that the knife actually reached the pope and cut him was not known until now.

“I can now reveal that the Holy Father was wounded. When we got back to the room (in the Fatima sanctuary complex) there was blood,” Dziwisz says in the documentary.

The pope carried on with the trip without disclosing his wound.

Krohn was arrested and served several years in a Portuguese prison before being expelled from the country.

The documentary combines on-camera narration by York, interviews with Dziwisz, historical footage and re-enacted segments of the pope’s life played out by actors.

It includes video of his last public appearance from his window overlooking St Peter’s Square, when, debilitated by Parkinson’s disease and other maladies and overcome with emotion, he did not manage to pronounce any words.

Dziwisz says that when the pope, who had undergone a tracheotomy to help him breathe, was wheeled back into his apartments, he regained some strength and managed to whisper: “If I can’t speak any more, it’s time for me to go.”

He died several days later on April 2, 2005, aged 84.

The 66-year-old York, who acted in Cabaret, Romeo and Juliet and a dozens of other films and television productions, said he felt “awe” at being part of a production involving John Paul.

“He had an extraordinary ability to communicate with people -- I think its called star quality and as a pope he had star quality in abundance,” he told Reuters in an interview.

The documentary was shot in Rome, the Vatican and the cities in Poland where the John Paul was born and worked as a priest, bishop and cardinal before his election to the papacy in 1978.