Justin and Jessica
Justin Timberlake and Jessica Biel are planning a big summer wedding. REUTERS

Justin Timberlake and Jessica Biel have been engaged for nearly four months now, but the two have remained mum on details of their upcoming wedding. Biel, 29, debuted her engagement ring only in late February, at an after party for the Saturday Night Live crew.

Now, details of the big day have emerged, thanks to a source close to the famous couple.

Justin and Jessica are planning a big [summer] wedding . . . Jessica initially wanted a smaller, more intimate wedding, but Justin from the beginning wanted a big wedding and that's what they have decided on, the source told People this week.

The summer wedding will also include all their friends, the source added.

Timberlake, 31, popped the question in late December, when the two were vacationing in Jackson, Wyoming.

While the two have yet to officially confirm their engagement, Timberlake's grandmother Sadie Bomar was the first to verify the happy news.

He called me on Christmas Day and told me he's engaged . . . the family loves Jessie . . . she's a very sweet girl, Bomar told Gossip Cop in January.

In February, Biel and Timberlake joined SNL cast members at a party in New York, after Timberlake made a surprise appearance on the show (channeling Justin Vernon of Bon Iver and a boom operator from the Bronx). At the party, the couple stayed close and were very lovey, kissing a few times in front of the crew, a source told Us Weekly.

Biel, meanwhile, flashed her sparkly accessory to Amy Poehler and Kristen Wiig, who loved the ring and chatted her up about it, according to the New York Daily News.

What about the dress?

Biel has yet to pick out her dress for the big day, but has been very involved in the wedding plans, the source told People, adding that Justin has promised her the best day ever.

In addition to her big summer wedding, Biel has a busy professional year lined up. The actress has at least three films coming out this year, including Total Recall with Colin Farrell and Kate Beckinsale, and Playing The Field with Gerard Butler, Catherine Zeta-Jones and Uma Thurman.

Timberlake, meanwhile, has been busy filming Inside Llewyn Davis and Trouble with the Curve. He is rumored to be starring as Finnick Odair in the next Hunger Games film adaptation, Catching Fire.