The former N*Sync star is said to have proposed to Biel during a holiday in Rome last week. They will marry in the next 18-months.

"He is besotted with Jessica and wants to make an honest woman of her,” a source told the Sunday People.

"He planned to propose in Rome because it is such a romantic city. Jessica is over the moon and looking forward to a huge wedding. She can't wait."

Timberlake has previously had high profile relationships with actress Cameron Diaz and Britney Spears.

(by Jason Gregory)