Britney Spears wants another baby. The singer - who already has two sons, Sean Preston, five, and four-year-old Jayden James, with ex-husband Kevin Federline - is said to be keen to have a child with partner Jason Trawick and wants them to start trying as soon as her world tour finishes at the end of the year.

"She's always wanted a big family but also wants to prove to herself and to her family she is a good mother. She wants another chance to put things right. Now she's finally had the green light from Jason, she can't wait," said a source.

Earlier this year, it was claimed Britney - who temporarily lost custody of her boys to Kevin, following a very public breakdown in January 2008 - had got engaged to Jason after her former manager popped the question.

The "I Wanna Go" singer - who already has failed marriages to Kevin Federline and Jason Alexander under her belt - was thrilled when Jason filled the entire ground floor of the couple's Los Angeles mansion with candles and roses, before presenting her with a diamond flower-shaped ring.

"She's on cloud nine. Britney is desperate to settle down again and have more children. But she is very traditional and didn't want to start a family with Jason until they'd tie the knot, an insider said."

Britney - whose first union to childhood friend Jason Alexander was annulled just 55 hours after they married in Las Vegas in 2004 - is now said to be planning a "low-key" ceremony in Hawaii once she has completed her upcoming world tour.