Kim Kardashian West has slammed Tristan Thompson for allegedly cheating on her sister Khloe Kardashian.

The 33-year-old reality star recently welcomed a baby girl named True with the NBA star just days after a video emerged of him seemingly leaning in for a kiss with another woman, and her older sister Kim has now described the situation as ''f***ed up''.

She said: ''Poor Khloé. Like, I don't even know how to describe it besides it's just so f***ed up. We really were rooting for Khloé. And we still are. She's so strong and she's doing the best that she can. It's a really sad situation, all over.''

The 'Keeping Up with the Kardashians' star has decided to take the high road though and won't be bad mouthing the 27-year-old Cleveland Cavaliers player too much, for the sake of her 15-day-old niece.

Speaking during an appearance on 'The Ellen Degeneres Show', Kim, 37, added: ''I kind of made this rule with my brother [Rob Kardashian] - if there's a baby involved, I'm going to keep it cute and keep it classy and not talk too bad. Well, I'm going to try not to say anything so negative because one day, True is going to see this and you know, it's so messed up.''

As of the time of writing Khloe is yet to confirm whether or not she plans to stay with Tristan following his alleged scandal, and sources recently claimed she hasn't ''given up'' on their romance just yet.

An insider said: ''She has one foot out the door but is also holding on to the fact that her and Tristan can make it work. She hasn't given up on him yet, but also hasn't really been focusing on their relationship. When they see each other, it is all about the baby and parenting together. Khloe has fallen in love with him all over again, watching him be a dad to True, but [she also] knows she needs to really take a step back and make the right decision.''