The couple have been friends for a long time and announced that they were dating in April this year.
"Kanye's saying the ring will 'blow her away', and it will 'out-bling all the other bling'. He says it will make her old engagement rings look like kids' toys," a source said.
Kardashian was previously married twice. Her last marriage to Basketball player Kris Humphries lasted for only 72 days.
