Ashton Kutcher and Mila Kunis are to finally seal their relationship by tying the knot today, according to a US report.

The Hollywood stars became engaged last year and welcomed their first child, a daughter named Wyatt, in October.

They were recently rumoured to have exchanged vows in secret after Kunis was spotted wearing a band on her left hand, but a new report suggests the couple will officially wed at a private mansion in Los Angeles over the Independence Day weekend.

A source tells New York Post gossip column Page Six: "Details are being held close to the vest and were expected to go out to guests 24 hours or less before the wedding. It is going to be a very small and intimate affair with friends and family."