Viggo Mortensen is beginning to feel his age. The quietly eccentric actor who won a worldwide fan following as the heroic warrior Aragorn in the Lord of the Rings trilogy is turning 50, and admits ruefully: "I'm starting to notice I'm slowing down a bit.

"There were a lot of times when I would say, 'I'm only going to get three hours' sleep, so I might as well stay up the rest of the night.' Now I tend to sleep those three hours."

The multi-talented Mortensen, a Renaissance man if ever there was one, needs as many waking hours as he can get to accommodate his cultural activities in the fields of art, poetry and music, not to mention his acting work - he stars in three vastly different films due for release in the next few months.

His paintings and photographs have been exhibited in galleries in New York and Los Angeles, and he has published 10 books of poetry, photography and painting. A talented pianist and composer, he has collaborated with the guitarist Buckhead on seven albums and his singing is featured on The Lord of the Rings: The Return of the King soundtrack and on the DVD edition of The Fellowship of the Ring.

The famously self-effacing Mortensen - his Lord of the Rings co-stars nicknamed him No-Ego Viggo - is the star of Appaloosa, a western in which he stars with Ed Harris and Renée Zellweger.

When I meet him he speaks so quietly it is difficult to hear him, and he is a master at guiding the conversation away from himself, although he is unfailingly courteous.

A keen horseman and outdoorsman, he took the role in Appaloosa, a classic western with bad guys, Indians and laconic lawmen, because the subject matter appealed to him.

"I like being outdoors, I like landscapes, and I like riding horses," he says. "I get along with them and like them as creatures.

"I also like the classic western movies, but I would never do a western just to be in one, because thousands that have been made since the beginning of the movies are terrible - really badly acted and badly designed.

"Appaloosa respects the genre and is well written and well acted and that's why it works."

He and Harris, who also directed, and with whom he worked in A History of Violence, play lawmen hired to rid a town of the tyranny imposed by a bad-guy rancher (Jeremy Irons) and his men.

"Ed and I would joke about it sometimes when we'd be on our horses out in these beautiful landscapes, saying, 'Boy, this is amazing. We're getting paid to do this thing we used to play at when we were little.'"

Mortensen, who received a best-actor Oscar nomination for his role in Eastern Promises, will also soon be seen in The Road, a film based on Cormac McCarthy's post-apocalyptic novel that was initially rejected by Hollywood as being too bleak and grim for the screen.

In it he stars as an exhausted but loving father guiding his son across a desolate America following an unspecified cataclysm.

"I've done a lot of movies where there's a certain amount of physical effort and commitment involved, but I've never worked on a movie that was as much of a marathon emotionally," he says.

"But, if it wasn't hard to shoot and kind of painful a lot of times on some level, then we would probably have been doing it wrong, so my hope is that the end result will be in the spirit of the book. In other words, it will probably be upsetting to watch, but it will also in a brutal way be beautiful. That's my hope for it."

He has a particular fondness for the third movie he has awaiting release, Good, based on the play by C P Taylor, even though the starring role of bookish intellectual John Halder could not be further from the men-of-action he usually plays.

He first saw the play, about a German literature professor who gets seduced into the Third Reich after writing an essay on the benefits of euthanasia, when he was in London 25 years ago to audition for a role in a movie he did not get.

"I liked it very much, and it made a strong impression. But then I more or less forgot about it until I read the script a quarter of a century later and it seemed familiar. I thought it was a good way to make a circle out of the experience so many years later."

An ardent football fan, Mortensen is wearing a red shirt bearing the logo of his favourite team, San Lorenzo in Argentina, where he spent 10 years of his childhood before moving to Copenhagen with his Danish father after his parents divorced [sic].

His itinerant childhood gave him the gift of multi-lingualism (he speaks fluent Spanish, Danish and French, as well as a smattering of Swedish and Norwegian) and ignited in him an intellectual curiosity about the world, which he believes has informed his work both as an actor and artist.

In the early Eighties, he took drama classes in New York and his first film roles, in Woody Allen's The Purple Rose of Cairo and Jonathan Demme's Swing Shift, ended up on the cutting room floor.

But he persisted and landed a small part as an Amish farmer in the 1985 drama Witness, followed by a series of roles in bad films such as American Yakuza and Young Guns II until 1991 when Sean Penn cast him as a volatile Vietnam veteran in The Indian Runner.

His career took off then, with roles in Brian de Palma's Carlito's Way, as the artist-lover opposite Gwyneth Paltrow in A Perfect Murder, which featured his own paintings, and A Walk on the Moon with Diane Lane, who said of her co-star: "He's a man of mystery, for sure."

Then came the Lord of the Rings trilogy, followed by Hidalgo, the true story of a horse race across the Arabian desert, and A History of Violence, for which many critics thought he was unlucky not to be nominated for an Oscar.

David Cronenberg, who directed him in A History of Violence and Eastern Promises, says of him: "Viggo has the charisma of a leading man and the eccentricity and naturalistic presence of a character actor."

Mortensen, who likes to go barefoot, lives in the wooded Topanga Canyon area of Los Angeles and has a 20-year-old son, Henry, from his 10-year marriage to Exene Cervenka, the singer with the punk band X, which ended in 1997.

With part of his earnings from The Lord of the Rings, he founded a publishing house, Perceval Press, to help other artists by publishing works that might not find a home in more traditional publishing venues.

Ironically, as he devotes more of his time to his personal pursuits and interests, he is increasingly in demand for movie work, although he would not mind if he never went in front of a camera again.

"I've had a really good run lately, not just with these three movies coming out but the last two before that and three before that," he says.

"I've made a lot of interesting ones and I've worked with some really good people. Not in a disrespectful way, but now I could kind of take it or leave it to be honest with you. I've felt that way for quite a while."

Viggo Mortensen, who is happier riding his horse than walking a red carpet, has poetry to write, art and music to create, books to publish and soccer to watch.

But Hollywood is hoping he will still find time to fit in the occasional movie role.