Bradley Cooper is reportedly planning to marry Suki Waterhouse on his 40th birthday next year.

The 'Hangover' hunk is keen to tie the knot with the 22-year-old model - whom he has been dating since March last year - in the US on their joint birthday on January 5.

A source told the Daily Star newspaper: ''Bradley wanted to wait until his 40th before getting hitched as he's been married before. It's very important for him now that they seal their love.''

The loved-up couple have already begun planning their big day and are keen for it to be an intimate affair in front of their close friends and family.

The source explained: ''Bradley and Suki spend a lot of time daydreaming and planning their nuptials.

''They know they want to get hitched in the States, most likely LA, because they want it to be hot. But it's likely to be a very small, private affair.''

The pair sparked rumours they had got engaged earlier this month after they were spotted wearing matching rings on their wedding finger as they left The Chiltern Firehouse in London.

Meanwhile, Bradley was previously married to actress Jennifer Esposito in 2006, but just four months later they announced that they were divorcing.

He then went on to date Renée Zellweger from 2009 to 2011, before striking up a relationship with Zoe Saldana from December 2011 to January 2013.

Suki, on the other hand, has had previous relationships with The Kooks' frontman Luke Pritchard and Miles Kane.