Kim Kardashian is reportedly worried Khloé Kardashian will upstage her at her upcoming wedding.

The 'Keeping Up with the Kardashians' star, 33, thinks her younger sister, 29, looks better than ever after slimming down following her split from Lamar Odom in December, but is afraid she will ''pull a Pippa Middleton'' and draw attention away from her on her and Kanye West's special day in Paris on May 24.

A source told In Touch magazine: ''She hates that people have started calling Khloé the hotter sister, so Kim's obsessed with making sure that she is the sexiest Kardashian at her wedding.''

Khloé has lost 30 pounds over the past six months after upping her workouts to five times a week when her marriage to Lamar began to crumble amid rumours he was addicted to cocaine and cheated on her with multiple women last year.

The insider added: ''She's jealous of Khloé ever since she lost a ton of weight. Kim doesn't want to be upstaged at her own wedding. Kim is working out and getting laser treatments to make sure she's the thinnest. Khloé won't steal her thunder.''

Meanwhile, Kim is also concerned that her sister will try to bring her new boyfriend, French Montana, to her nuptials.

The friend said: ''This day is supposed to be about her and Kanye. Kim wants this to be her dream wedding. She's flipping out because she thinks Khloé could derail it all.''