Britney Spears' sons won't kiss her in front of their friends anymore because they are "getting what's cool and what's not".

The international superstar has sons Sean Preston, seven, and six-year-old Jayden James from her marriage to Kevin Federline.

Speaking on Ryan Seacrest's KIIS-FM radio show, Spears said her boys think she is becoming more embarrassing as they are getting older.

She explained: ''My sons are six and seven, so they're just now getting to the stage of where you can't kiss mommy in front of your friends and all that kind of stuff. They're getting what's cool and what's not.''

Spears recently unveiled her new song that will feature on the soundtrack for the upcoming 'Smurfs' movie sequel. 'Ooh La La' received its first play on Ryan Seacrest's radio show and she also opened up about why she took on the project in the first place.

She said: ''The main reason why I did it was because my boys. They're obsessed with 'The Smurfs'. We've seen 'The Smurfs' movie a million, trillion times and they were told they could be in the music video.

She added: ''My oldest son, Preston, was right on cue every time they would tell him to do something in the video. They play themselves. But when we did the actual shoot of the video, I didn't see them. I was in hair and makeup, so later on I got to see what they actually did on camera - and it was adorable!''