Justin Bieber has confessed he was terrified when he first kissed girlfriend Selena Gomez.

The "Baby" hitmaker, 18, stepped out with the 20-year-old actress in February last year, confirming months of speculation they are dating, but he remains reluctant to discuss the relationship.

In a rare candid moment, Bieber has told how he was a bag of nerves when he first made a move on the former "Wizards of Waverly Place" star - but he was left smitten by the smooch.

Bieber tells We Love Pop magazine, "It was scary and spontaneous and it was just awesome... (It was) the best (kiss) of my life."