Kim Kardashian's engagement ring reportedly cost $2 million.

The 30-year-old beauty announced her engagement to basketball star Kris Humphries earlier today (25.05.11) and it has now been revealed the 20.5 carat Lorraine Schwartz diamond ring set Kris back a huge sum of money.

According to gossip website TMZ, the ring is worth almost half as much as Kim's Beverly Hills mansion and is valued at $2 million.

A source added: "The ring is of the highest clarity and colour."

The stunning piece of jewellery has impressed everyone, including Kim's younger sister, Khloe, who joked it made her engagement ring from husband Lamar Odom look tiny.

She tweeted: "OMG I die for you! Kims ring gave birth to my ring! LOL but my ring is perfection! Its from my Lammy. (sic)"

Khloe also took to her twitter page to give her congratulations to Kim and Kris, who have been dating for around six months.

She wrote: "I can't believe I was able to keep this a secret but now I can scream all I want about it! Kim is engaged!!!!!!!!!!!!!!!!!!!! OMG!!!!!!!!!! (sic)

She then added: "Kimmie I love you so much!!!! I would do anything in the world for you!!! Seeing you this happy in your life makes me smile daily! (sic)"

Kim's older sister, Kourtney, also took to twitter to speak of her joy about the engagement.

The mother-of-one wrote: "My sister is engaged!!! I'm squealing with excitement! The princess has found her prince. I am so happy because @KimKardashian is happy! (sic)"