Justin Timberlake is reportedly planning to propose to girlfriend Jessica Biel.

The 'SexyBack' singer - who has been dating Jessica for over a year - was seen shopping for engagement rings at famous New York jewelery store, Tiffany and Co.

An onlooker said: "Justin was really taking his time looking round the rings. He made the staff get a couple out of the cabinets so he could properly look at them."

"He didn't buy anything but told the manager he would think about it."

Jessica recently revealed she and Justin much prefer snuggling up with the board game Scrabble than going out drinking and dancing.

She said: "We do a lot of dinner parties and we play board games. I absolutely love Scrabble!"

Justin and Jessica have been reluctant to speak openly about their relationship.

When 26-year-old Justin appeared on TV show 'The Oprah Winfrey Show', he refused to talk about 25-year-old Jessica, only saying: "I'm dating someone but all I can tell you is she smells lovely!"