Actor Stuart Townsend will take time out from Hollywood this weekend to protest against the routing of the M3 motorway near the Hill of Tara, campaigners said.
The Irish star, who recently sparked speculation he had married his girlfriend actress Charlize Theron, is expected to join demonstrators at the Dáil on Saturday.
Hothouse Flowers singer Liam Ó’Maonlaí will also turn out in Dublin to back the show of opposition to the destruction of parts of the archaeologically-rich Tara valley.
Harpists will play outside Leinster House, in a symbolic gesture of Irish heritage, as a petition to Minister for the EnvironmentJohn Gormley demanding an alternative to the current plans is handed over.
The 36-year-old Townsend, from Howth, in north Co Dublin, is to join his friend aerial photographer John Quigley on Sunday for another demonstration at the Hill of Tara.
The pair are to fly over the ancient Co Meath landmark to take photographs of hundreds of campaigners forming a “human harp”.
“Ireland is unique in having a musical instrument, the harp, as its national emblem,” said a spokesman for campaigners Tarawatch.
“This indicates the primacy of the harp in Irish culture. The sites currently under threat are inextricably linked with the harping and bardic traditions for more than 2,500 years.”
Other harpist events are to take place outside Irish consulates in New York, Chicago, and Los Angeles at the same time as the Dublin protest, according to protesters.
Irish Pulitzer prize-winning poet Paul Muldoon and Irish Grammy award-winning singer Susan McKeown are expected to be among other artists at an event in New York.