Simon Cowell "worries" he's too old to have children.

The 50-year-old star - who has previously hinted that he would be ready to start a family with his make-up artist fiance Mezhgan Hussainy - admitted time was against him if he planned to have children in the future.

Speaking to the US TV chat show host Oprah Winfrey, he said: "I... you know, I worry about that because of my age. You know, when I was younger, my dad used to play soccer and, you know, games with me and I worry - I worry that if I was 70. it worries me a bit."

The 'X Factor' star admitted he probably doesn't have the time - or patience - for a baby and joked it would be easier if a child could be born a little older.

He said: "Not that it's absolutely out of the question... if they could be born at the age of five. maybe. Maybe that will happen."

The media mogul also made the admission that despite all his TV success, he still suffered periods of depression where he reflected on "horrific" past decisions he'd made.

He said: "I get very, very down. I've made some absolutely horrific mistakes in the past."

Only recently, Simon spoke about his future plans with 36-year-old Mezhgan and claimed he was "torn" about the decision to have children.

He said: "I'm kind of torn because I'm a bit too old to have kids, but then again I think it would be important to have a lot of mess around in the future."