French movie director Francois Ozon tackles the thorny issue of euthanasia in his latest movie at the Cannes Film Festival, with a story of two sisters grappling with their sick father's desire to end his life.

In "Everything Went Fine", Ozon does not take sides in the debate, preferring to let the siblings' struggle unfold and leave audiences to ponder what they would do in their situation.

"I don't think the film is either for or against (euthanasia). It proposes to the viewers a story that is very personal, and each one faces his or her own questions about it, on life, on death," Ozon told reporters in Cannes on Thursday.

The film starring Sophie Marceau is in the main competition at the world's biggest film festival being held on the French Riviera later than usual, after the coronavirus pandemic forced organisers to cancel it in 2020 and postpone it this year.

Spain became the fourth European Union country to allow assisted dying in March this year, joining Belgium, Luxembourg and the Netherlands, while Switzerland also has similar laws.

Euthanasia is still banned in France, although under a law from 2016, terminally ill patients have the right to be put into continuous deep sedation.

Ozon, a prolific filmmaker who released "Ete 85" last year, said he had discovered a world he knew little about after choosing to adapt the true story from a book by late writer Emmanuele Bernheim, who worked on several of his screenplays.

"This is what horrified me, to see that the state, society, the medical system do not take care of this, and that it's up to the children to organise it," Ozon said.

"Everything Went Fine" also features a star turn by Andre Dussollier as an 85-year-old who has a stroke, paralyzing him in one arm, and who calls on his daughters to help him end his life.

The sisters are torn between the hope that he will change his mind, as he displays flashes of humour or gets excited about his grandson's upcoming clarinet recital, and a growing sense of duty as they come to terms with his stubborn desire to die.

Punctuated by lighter moments, such as when the irascible Andre expresses horror at the idea of being buried near the in-laws he hated, the film builds tension as the sisters wonder whether they can go through with their plan.

"This film has a dimension that urges us to think about this," Marceau told a news conference. "We don't really like the idea of this kind of death, but at some point we must get organised about this thing."

Frenchman Alain Cocq, who fought for years for the right to euthanasia at home, died in June this year in a medically assisted suicide in Switzerland at the age of 58, in a case that reignited the debate in France.