Justin Timberlake and Jessica Biel to marry this summer?

Recording artist Justin Timberlake speaks during a Panasonic news conference for the 2012 International Consumer Electronics Show (CES) in Las Vegas, Nevada, January 9, 2012. [Photo/Agencies]

Justin Timberlake and Jessica Biel are set to marry this summer.

The couple - who have been dating on and off for five years before getting engaged in December - will reportedly tie the knot at a private estate later this year with Jessica planning to wear a custom made Monique Lhuillier dress.

A source told USmagazine.com: ''The big day's this summer at a private estate. Monique Lhuillier is her number one choice for the dress.''

Despite refusing to confirm their engagement, Jessica showed off her engagement ring at a party in New York earlier this month, with witnesses guessing it could be vintage.

A source said: ''It wasn't huge. It looked vintage and might have been custom made.''

Justin, 31, is said to have proposed to the 31-year-old actress last year during a pre-Christmas break in Jackson, Wyoming, after they reunited following a three-month split.

A source said at the time: ''Justin knows how much she loves snowboarding and the mountains, so it was the perfect place.

''This was the basis for getting back together. When they reunited they had a conversation about taking the next step.''

The couple - who have dated on-and-off for the past four years - are believed to have then celebrated their engagement with their family and friends at Justin's home in Big Sky, Montana.