Hollywood actor Robin Williams has been lined up to perform the irreverent song Blame Canada from the South Park movie at Sunday's Oscars ceremony.

Blame Canada - taken from South Park: Bigger, Longer & Uncut - is one of the five songs shortlisted by the Academy in the original song category. Tradition holds that all the best song nominees are performed during the awards.

The lyrics to Blame Canada rile against censorship and Williams will have to negotiate his way around a number of expletives - despite the song being acknowledged as one of the cleaner tunes from the film.

However, the notoriously zany Williams is unlikely to be daunted by the challenge. The star of Good Morning Vietnam and Mrs Doubtfire, Williams is known for his sharp improvisation skills and ability to tackle difficult roles.

Dilemma

In the song, angry parents and community leaders in the US condemn Canada for exporting a corrupting obscenity-laced movie for children.

Aside from bad language, the song also takes a swipe at famed Canadian singer-songwriter Anne Murray.

The surprise nomination of Blame Canada has posed a dilemma for the producers of the Academy Awards and US broadcasters ABC.

ABC has told the Academy the song needs to be cleaned up or have its profanities bleeped out so that it can be broadcast without embarrassment.

Bruce Davis, executive director of the Academy of Motion Picture Arts and Sciences, said:

"I'm not aware that we have ever had quite that problem before. Everybody knew what the movie was like, and part of the joke was that the songs were scatological and foul to the extreme."

But the song's composer Marc Shaiman, who wrote the song with South Park co-creator Trey Parker, says they are not taking these concerns too seriously.

"We'll figure out a creative way to make light of whole situation," said Shaiman.

"It's a song about censorship from a movie about censorship, so the irony is not lost on any of us that we're being asked to censor the song."

Williams' rendition of Blame Canada will be up against much tamer competition for best song.

British pop musician Phil Collins will perform his song You'll Be in My Heart from Tarzan. US pop stars Gloria Estefan and 'N Sync will sing songwriter Diane Warren's Music of My Heart from the Meryl Streep movie Music of the Heart.

Aimee Mann will sing her tune Save Me from Magnolia. While veteran singer Randy Newman, nominated for his 13th Oscar, will join Sarah McLachlan in performing his song When She Loved Me from Toy Story 2.