Rhys won't imitate Firth's Mr Darcy
The 38-year-old Welsh actor will appear as Fitzwilliam Darcy in BBC One drama Death Comes To Pemberley, an adaptation of PD James's sequel to Pride And Prejudice.
Matthew, whose new drama tells the story of Elizabeth Bennet, played by Anna Maxwell Martin, and her husband six years after they married, admitted that "playing an iconic literary hero is always a little problematic".
He told the Radio Times: "Coupled with that, the fact that the aforesaid iconic literary figure has been immortalised by Academy Award-winner Colin Firth makes for a louder gulp."
He said his Mr Darcy would be "more mature" and "a family man", adding: "I can wholeheartedly say I won't be competing with Mr Firth emerging from a lake in a dripping white shirt - thankfully - because I don't think anyone can top him."
Last month, Colin's appearance as he emerged from a lake in Pride And Prejudice was named the most memorable moment in British TV drama. Other actors who have played the role of Mr Darcy include Laurence Olivier in a 1940 film adaptation, and Spooks star Matthew Macfadyen in Joe Wright's big-screen adaptation in 2005.
Matthew, who is well known in the US thanks to TV roles in The Americans and Brothers And Sisters, said of playing an English gentleman: "Strangely, I find an American accent easier than a posh English one as I always feel a lot more of a fake playing RP (received pronunciation). I feel like I'm being Lord Snooty or that Harry Enfield character (Tim Nice-But-Dim)".
The star also hinted that he had no intention of settling down.
"My mates who are in LA with their families or girlfriends have one main consideration: where does it shoot and for how long? I don't have those considerations because I'm single. It's lucky in a way - that I'm a bit late starting a family - not that my mum's happy about it," he said.