Nicole Kidman has sparked speculation she could be heading down the aisle with boyfriend Keith Urban, after being photographed with a diamond ring on her engagement finger.

The actress has yet to confirm she is even dating country star and fellow Australian Urban, but friends say the pair have become closer and closer since they were first spotted together last year (05).

Kidman flashed the ring as the pair left a New York hotel together yesterday (05JAN06).

The couple, who are both 38, have been spending New Year in the Big Apple after enjoying Christmas with Urban's family in Nashville, Tennessee.