(Cover) - EN Showbiz - Justin Timberlake has sparked engagement rumours after he was spotted ordering a ring believed to be worth $500,000.

The singer-and-actor has been dating fellow Hollywood star Jessica Biel, 28, for around four years, but they have been plagued by rumours they are on the verge of splitting. Neither talks about their romance in public, although Jessica has said the rumours dont affect her as she ignores them.

The pair are now said to have put any rocky times behind them, and it is thought 30-year-old Justin is on the verge of proposing. He has reportedly designed his own engagement ring for Jessica, which has set him back around $500,000.

The ring is big enough to sink a ship, a source told National Enquirer.

Justin is said to be planning a romantic proposal on Valentines Day later this month.

The star has had high-profile romances with women including Britney Spears and Cameron Diaz, and last year he joked he had to date a lot of different people to ensure he met The One.

He revealed he places honesty above everything else in a relationship, and he has to know he can trust his partner implicitly.

First of all honesty - no games, he said about his romance rules. And I don't begin a relationship inconsiderately, because I have to build up trust first. Then I devote myself totally. I am very romantic but I want to be able to laugh as well. If I sing about unconditional love I know it first-hand. (C) Cover Media