Buzz Aldrin appeared to criticize Neil Armstrong biopic First Man for leaving out the planting of the American flag on the Moon.

The 88-year-old, who was the second man to set foot on the Moon, on Sunday tweeted a picture of the flag planted after the landing in 1969.

He captioned the photo: 'Proud to be an American.' Aldrin also re-tweeted a photo of him saluting next to the same picture.

It is an apparent dig at Oscar-winning director Damian Chazelle's controversial decision not to include the planting of the flag at the end of his critically acclaimed movie.

The film is not kind in its portrayal of Aldrin, with Corey Stoll's performance painting him as an 'obnoxious loudmouth' and 'so blunt about his ambition that no one can stand him.'

Other reviews described Stoll's Aldrin as a 'swaggering hothead' who is 'cynical, mouthy and insensitive' while one reviewer said his appearances were so scarce that he was all but left out of the film.

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Aldrin, who was the second man to land on the moon after crew-mate Neil Armstrong, tweeted a picture of the flag planted after their landing in 1969

Proud American: Aldrin also re-tweeted a photo oh him saluting next to the same picture

First Man – from the Oscar -winning director of La La Land Damian Chazelle – opened the Venice Film Festival on Wednesday to criticism that it deliberately downplayed American patriotism. Pictured: The flag on the moon in 1969

The film is not kind in its portrayal of Aldrin, with Corey Stoll's (centre in the film) performance painting him as an 'obnoxious loudmouth' and 'so blunt about his ambition that no one can stand him.'

Starring Ryan Gosling as Armstrong, the film begins in 1961 as the US trails the Soviet Union in the space race and takes viewers up to the Moon landing in 1969. Pictured: Stoll as Aldrin

First Man, tipped to win big at the Oscars, opened the Venice Film Festival on Wednesday to criticism that it deliberately downplayed American patriotism.

Starring Ryan Gosling as Armstrong, the film begins in 1961 as the US trails the Soviet Union in the space race and takes viewers up to the Moon landing in 1969.

But it came under fire for not including the moment the astronauts planted the American flag, with Gosling defending the decision by saying the achievement 'transcended countries and borders.'

Marco Rubio was among the politicians to weigh in, tweeting: 'This is total lunacy. The American people paid for that mission,on rockets built by Americans,with American technology & carrying American astronauts. It wasn’t a UN mission.'

Canadian actor Gosling said he believes the moon landing was widely seen as a 'human achievement' and that's what the film reflects.

He added that Armstrong, who died in 2012, was 'extremely humble' and deferred focus from himself to the 400,000 people who made the Apollo 11 mission possible.

Ryan Gosling at the premiere of First Man in Venice. The film is not kind in its portrayal of Aldrin, with Corey Stoll's performance painting him as an 'obnoxious loudmouth' and 'so blunt about his ambition that no one can stand him.'

First Man begins in 1961 as the US trails the Soviet Union in the space race and takes viewers up to the Moon landing in 1969. Pictured, Gosling in the film

In response to the criticism of the flag, Gosling said that the Moon landing is an achievement that 'transcended countries and borders.' He also joked that he may be biased because he is Canadian. Chazelle is French-Canadian

The reviews: How Buzz Aldrin is portrayed The Guardian: 'Aldrin is - rightly or wrongly - shown as an obnoxious loudmouth.' Variety: Stoll plays 'the spiky tell-it-like-it-is Buzz Aldrin, who’s so blunt about his ambition that no one can stand him.' Daily Mail: Aldrin is Armstrong's 'spiky, insensitive colleague' The Times: Aldrin is 'the comedy relief to Gosling’s straight man)' BBC: 'You see almost nothing of Buzz Aldrin' The Wrap: 'Corey Stoll’s cynical, mouthy Buzz Aldrin' Hollywood Reporter: 'Bluntly opinionated Aldrin' Slant Magazine: 'Buzz Aldrin is portrayed as a swaggering hothead who seems to view the whole enterprise as a high-stakes dick-measuring contest' Advertisement

'He was reminding everyone that he was just the tip of the iceberg – and that's not just to be humble, that's also true,' Gosling explained.

'So I don't think that Neil viewed himself as an American hero. From my interviews with his family and people that knew him, it was quite the opposite. And we wanted the film to reflect Neil.'

Gosling also joked that he may be biased because he is Canadian. Chazelle is French-Canadian.

The decision to place a US flag on the Moon was controversial at the time with debates over whether a United Nations flag should be used instead.

Armstrong himself said that his job 'was to get the flag there' and he was less concerned about what flag it should be.

He said Congress had decided that the Moon landing was a US project.

Co-produced by Steven Spielberg, First Man - which also stars Claire Foy as Janet Armstrong - is based on a 2005 biography by historian James Hansen.

It has scored rave reviews and is tipped to win big at the Oscars.

First Man is one of 21 movies in competition for the Golden Lion at the Venice Film Festival which will be awarded on September 8.