Robert Pattinson doesn't want to ''devalue'' his relationships by talking about them.

The 32-year-old actor - who previously romanced Kristen Stewart and FKA Twigs - is believed to be dating model Suki Waterhouse but doesn't want to open up about it because he doesn't want to go ''completely mad'' by blurring the lines between his personal life and his on-screen career.

Asked about Suki, he said: ''Do I have to [talk about her]?

''If you let people in, it devalues what love is. If a stranger on the street asked you about your relationship, you'd think it extremely rude. If you put up a wall it ends up better. I can't understand how someone can walk down the street holding hands, and it's the same as when I do it and a hundred people are taking your photo.

''The line between when you're performing and when you're not will eventually get washed away and you'll go completely mad.''

While his relationships with Kristen and Twigs didn't end well, he doesn't believe high-profile romances are doomed.

He told the Sunday Times' Style magazine: ''They were pretty long relationships, not like three months.''

The 'High Life' actor is close friends with Katy Perry and is impressed by the fact fame hasn't changed her.

He said: ''She's exactly the same. That's difficult to do.''

But Robert thinks it's funny that while the 'I Kissed A Girl' hitmaker has five letters from past presidents wishing her a happy birthday, the only recognition he's had connected to the White House was in 2012 when now-President Donald Trump tweeted to say he shouldn't take back Kristen after she admitted to cheating on him.

He said: ''It's so f***ing cool, like five presidents! I got a tweet.

''That's my equivalent. She gets five presidential letters. I get relationship advice in a tweet.''