Kristin Cavallari's engagement to Jay Cutler is back on.

The former 'Hills' star was dumped by the NFL player in July after being engaged for three months but they have now decided to give things another go, after rekindling their romance in September.

A source told Life & Style magazine: "Kristin is over the moon with happiness. She's already told her friends that the engagement is back on. They haven't set a new date yet."

Following their split, Kristin - has previously dated 'Laguna Beach' co-star Stephen Colletti and Brody Jenner, who she starred with in 'The Hills' - handed Jay back her engagement ring. Although she was devastated by the break-up, friends say Jay had been thinking about it for a while.

One said: "She noticed a change in him. He suddenly became more supportive of her career. Up till then, he'd always talked about it coming to an end once they got married. It was like Jay knew he was leaving the relationship and didn't want Kristin to miss out on great opportunities in Los Angeles."

The shock break-up came just a week after they held a party to celebrate their upcoming nuptials with Kristin tweeting: "Thx to all my amazing friends for making my engagement party a blast last night! (sic)"