Britney Spears claimed she aborted Justin Timberlake's baby because her then-boyfriend "wasn't ready" to be a father

In an excerpt from her upcoming memoir 'The Woman in Me' published by People magazine, Britney wrote: "It was a surprise, but for me, it wasn't a tragedy. I loved Justin so much. I always expected us to have a family together one day. This would just be much earlier than I'd anticipated.

"But Justin definitely wasn't happy about the pregnancy. He said we weren't ready to have a baby in our lives, that we were way too young."

The 41-year-old star - who went on to have sons Sean Preston, 18, and 17-year-old Jayden with ex-husband Kevin Federline - described having a termination as "agonising" and admitted if it had been solely her decision she'd have continued with the pregnancy.

She wrote: "If it had been left up to me alone, I never would have done it. And yet Justin was so sure that he didn't want to be a father.

"To this day, it's one of the most agonizing things I have ever experienced in my life."

The 'Gimme More' hitmaker first met Justin when they worked together on 'The All-New Mickey Mouse Club', which she was cast on when she was just 11 years old, and she recalled how she and the 'Can't Stop The Feeling' singer first locked lips during a sleepover.

She wrote: "Being in the show was boot camp for the entertainment industry: extensive dance rehearsals, singing lessons, acting classes, time in the recording studio, and school in between.

"The Mouseketeers quickly split into our own cliques, divided by the dressing rooms that we shared: Christina Aguilera and I were the younger kids, and we shared a dressing room.

"We looked up to the older kids - Keri Russell, Ryan Gosling, and Tony Lucca, who I thought was so handsome. And I quickly connected with a boy named Justin Timberlake.

"It was honestly a kid's dream - unbelievably fun, particularly for a kid like me. But it was also exceptionally hard work: we would run choreography thirty times in a day, trying to get every step perfect.

"[Once] at a sleepover, we played Truth or Dare, and someone dared Justin to kiss me. A Janet Jackson song was playing in the background as he leaned in and kissed me."

A spokesperson for Justin - who has two sons, Silas, eight, and Phinneas, three, with wife Jessica Biel - has yet to comment.