Venerable Hollywood actor Martin Sheen has publicly backed Barack Obama as the Democratic party's presidential nominee for the first time.

Campaign groups representing Obama and his rival Hillary Clinton had both previously approached the 67-year-old seeking his support.

"Both Obama and Clinton came to me for support," Sheen said in a BBC interview with Graham Norton.

"I haven't said this publicly before but I'm an Obama supporter," the 67-year-old said.

Sheen played idealised Democrat president Josiah Bartlet for seven seasons of hit drama The West Wing, which counted former presidents among its fans.

"Bill Clinton loved The West Wing and still calls me the president, so I have to be careful," the Apocalypse Now actor revealed.

Obama currently holds a slight lead over Clinton to win the right to challenge the Republican party's nominee John McCain to replace George Bush in the White House.

He is also widely believed to be the inspiration behind Barlet's fictitious successor Matt Santos, played by Jimmy Smits.

In an echo of the Illinois senator's mantra, Sheen said that America was "ready for change" and was confident of a Democratic win.

"It would be great if Obama and Clinton were both on the ticket," he continued.

And in a dig at former Republican president Ronald Reagan, he categorically ruled himself out of any future bid for the White House, saying that actors going to the polls leads to voters mistaking "celebrity for credibility".

24/04/2008 13:01:05