It's one of the most iconic films in movie history.

But Al Pacino has revealed he thought The Godfather would be a flop and had to drown his sorrows with his co-stars during filming.

Joined by Robert De Niro and Diane Keaton, the 77-year-old actor made the confession during a Q&A at the 45th anniversary screening at Tribeca Film Festival in New York on Saturday.

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Legends: Al Pacino (R) was joined by The Godfather co-star Robert De Niro on Saturday for the 45th anniversary screening of the movie at Tribeca Film Festival in New York

Speaking at Radio City Music Hall, the Oscar-winning actor admitted that one scene in particular lead to the worries - the wedding scene with Diane Keaton- which was filmed in artificial light as they were running behind schedule.

He explained: 'Diane and I in that wedding thing... I mean we got so loaded after that wedding scene.'

As Diane looked amused and shook her head, he continued: 'A lot of chaos going on there. We got back, and we started drinking and we were just talking about "where do we go from here? We're done. It's the worst film ever made."'

Leading lady! Diane Keaton was also in attendance, but appeared to take issue with Al's claims that they went out and got drunk after filming

Father and son: Pacino played Michael Corleone in all three films, while De Niro played the younger version of his father Vito in the second part

The family: Co-stars Diane Keaton, Robert Duvall, James Caan and Talia Shire were also on hand, as was its legendary director Francis Ford Coppola

Pacino played Michael Corleone in all three films, while De Niro played the younger version of his father Vito in the second part.

Co-stars Robert Duvall, James Caan and Talia Shire were also on hand, as was its legendary director Francis Ford Coppola.

Francis Ford Coppola's daughter Sofia, who had two uncredited roles in the first two films and played Michael's daughter in the third, was also there with husband Thomas Mars.

Other stars spotted at the screening and Q&A included Katie Holmes, Whoopi Goldberg, Peter Fonda and wife Margaret DeVogelaere.

As seen on screen: Al Pacino played Michael Corleone in the film series - the youngest son of the mafia don Vito Corleone who sets out to run his own mafia empire

In for the sequel: Robert De Niro played Vito Corleone in The Godfather Part II

On the screen: Diane Keaton played Michael's (Pacino) non-Italian girlfriend and his second wife and mother of his two children

Advisor: Robert Duvall played Tom Hagen, Don Corleone's informally adopted son, he is the family lawyer and consigliere

Brotherly love: James Caan played Santino 'Sonny' Corleone, Don Corleone's hot-headed eldest son and heir apparent to succeed his father as head of the Corleone family

Blushing bride: Talia Shire played Constanzia 'Connie' Corleone, the youngest child and only daughter of the Corleone family. Her wedding reception begins the film

The Godfather and The Godfather Part II are considered among the greatest films of all time. Both won the Academy Award for Best Picture, with Part II becoming the first sequel to ever do so.

Coppola was nominated for Best Director for the first in 1972 and won for the second in 1974.

Caan, Duvall and Pacino were all nominated for Best Supporting Actor for The Godfather, while De Niro won the award two years later for the second part. Pacino was also nominated for Best Actor that year.

The Godfather starred Marlon Brando and Al Pacino as the leaders of a fictional New York crime family. The story, spanning 1945 to 1955, chronicled the family under the patriarch Vito Corleone, focusing on the transformation of Michael Corleone (Pacino).

Pals: Whoopi Goldberg was spotted with Pacino

Child star: Sofia Coppola, who had two uncredited roles in the first two films and played Michael's daughter in the third, was also there with husband Thomas Mars

Easy rider: Peter Fonda was accompanied by wife Margaret DeVogelaere

Top class: The Godfather and The Godfather Part II are considered among the greatest films of all time

Accolades: Both won the Academy Award for Best Picture, with Part II becoming the first sequel to ever do so

Two in a row: Coppola was nominated for Best Director for the first in 1972 and won for the second in 1974

The greatest: Caan, Duvall and Pacino were all nominated for Best Supporting Actor for The Godfather, while De Niro won the award two years later for the second part. Pacino was also nominated for Best Actor that year

Fan: Katie Holmes also arrived for the 45th anniversary screening of The Godfather at the Tribeca Film Festival on Saturday night