Actress Nicole Kidman has said she chose to use a surrogate mother to expand her family because she "desperately" wanted another child.

Speaking on Australian television show '60 Minutes', she said: "We were in a place of desperately wanting another child. This opportunity arose for us, and I couldn't get pregnant."

"Children are children - you'll die for your children. And when you feel that as a parent - that's the unconditional love."

Kidman has two children with husband Keith Urban and two children from her marriage to Tom Cruise.