Kim Kardashian West insists Kylie Jenner ''didn't lie'' about having lip fillers.

The 34-year-old reality TV star thinks her 17-year-old half-sister, who recently confirmed she boosted the size of her pout with surgical injections after previously claiming it was the result of clever make-up, ''looks beautiful'' and says she contemplated the decision for some time.

The 'Keeping Up with the Kardashians' star said: ''She didn't lie, it took her a while to actually make that decision to do it and once she decided to plump them, she was still over-lining, then sometimes it would look too big, then she figured out to stop over-lining. She plumped them and she was happy with it. People think 'Oh my god she lied for so long - now she's finally come clean' but that's not really the case, it took her a while to do it.''

Kim also claims that Kylie, who is dating 25-year-old rapper Tyga, has never been happy with her lips.

She told 'Access Hollywood': ''At 10 and 11 years old she'd say 'Kimmy, how come my lips aren't as big as your guys?'

''So if it's going to make her feel better about herself, I'm all for it. I think she looks beautiful.''

The teenager decided to come clean on her family's E! reality series after her other half-sister Khloé Kardashian, 30, urged her to tell the truth.