Tyra Banks has undergone ''traumatic'' rounds of fertility treatment.

The 41-year-old supermodel - who has been with boyfriend Erik Asla for two years - admits she has found it ''difficult'' trying to conceive in recent years, and has undergone in vitro fertilisation (IVF) in the hope of fulfilling her dream to be a parent.

She said: ''When I turned 40, the one thing I was not happy about is that I did not have kids. I'm like, 'Damn, the clock is ticking!'

''When you're like, 'OK, I'm just going to do it,' then it's not so easy as you get older.''

''I've had some not happy moments with [IVF], very traumatic moments.

''It's difficult as you get older. It's not something that can just happen.''

The 'America's Top Model' host admits she regularly put off starting a family because of her work commitments.

She told People magazine: ''Since I was 24, I used to say every year, 'I will have kids in three years.'

''I kept saying it over and over again. Because my business is very entrepreneurial. I'm not for hire, so I have to do everything. I kept trying to find that time for that to happen.''

Despite her struggles, Tyra is trying to stay positive and won't give up her baby dream.

She said: ''I hope [for kids]. I don't just want one child. I want a litter! And I want to be the kind of mom where my child can come to me for anything.''