Kim Kardashian is allegedly "envious" of her sister's 'X Factor' USA job.

Relations between the 32-year-old 'Keeping Up With The Kardashians' star and her 28-year-old sibling Khloe are reportedly very tense since her younger sister secured the high profile presenting job last month.

Related: Khloe Kardashian to host 'The X Factor'

A source told Life & Style magazine that the reality TV star "has become deeply envious" of Khloe's job and it has already "led to some serious tension" in their family.

An insider said: "Kim and Khloe has been fighting lately because Kim is extremely jealous of Khloe's career. (Kim) feels like Khloe had become the breakout star of the family, and she hates it."

Khloe - who is married to Clippers basketball star Lamar Odom - previously revealed that her older sister had given her constructive criticism on how to improve her presenting skills.

She explained: "My sisters have already texted me tips, which I love. I love constructive criticism. I've never done this before, so I just think I can only get better - hopefully.

"My sister Kim was like, 'You did amazing, but don't yell so much!' I did notice at some points, I was like, 'Why did I just yell?'"

Earlier this week Kim admitted she would love to be her 17-year-old sister Kendall for one day because she admires her body.

Asked which celebrity's figure she most admires, she said: "My little sister Kendall. I'm like, 'I just want to be you for one day'. How are we even related?

"It's a struggle for me [to lose weight], constantly."