A ring on pop star Katy Perry's ring finger has sparked rumours that she may be engaged to singer-boyfriend John Mayer.

She stepped out with her beau for a romantic Valentine's Day dinner at Sunset Towers here Friday night, flashing the jewellery on her ring finger, reports eonline.com.

"They are really happy. They had the most amazing date night. They had a private booth at Bootsy Bellows and were very happy just to be together," said a source.