Italian President Giorgio Napolitano has asked Iran to spare an Iranian woman who faces death by stoning for adultery.

Italy is mobilised to prevent 'such a deeply harmful act against liberty and the sanctity of human life', Napolitano said Tuesday.

'The Italian government and institutions are strongly committed to saving this Iranian woman's life, and there is a public campaign which continues to gain momentum,' Napolitano said.

Sakineh Mohammadi Ashtiani has been sentenced to death by stoning for adultery and helping kill her husband.

The sentence is in suspension during the holy month of Ramadan, but there are fears the 43-year-old mother of two could be executed when Ramadan ends Friday.