Los Angeles- Sandra Bullock and boyfriend Jesse James have sparked speculation that they're planning to wed after they were spotted shopping for diamond rings.

The marriage would mark the third trip down the aisle for TV tough man James, while it would be the first for Bullock, who in the past has been romantically linked to Tate Donovan, Matthew McConaughey and Ryan Gosling, reports the website WebIndia123.

The star's representatives insisted that the two were at a jewellery store shopping for "gifts", said the report.

Witnesses, however, reportedly said the pair was seen at the Neil Lane store in Los Angeles on June 26, lingering over "a very large cushion cut" diamond engagement ring.

And sources have reportedly told America's Star magazine that as soon as James' divorce to porn star Janine Lindemulder is finalized, the pair will wed.