Britney Spears -- I Won't Make My Son Dance On Stage

Apparently Britney Spears heard Kevin Federline's threat loud and clear ... because she's backed off her comment that Sean Preston will join her on stage for her Vegas concert series.

Britney said in an interview during her big announcement last month ... "Preston will probably be on stage but I think Jayden would have a hard time with it."

The next day we got video of K-Fed ... and he made it clear, his 8-year-old would NOT be performing with Britney.

Britney's rep tells TMZ ... she was "joking" when she said Sean Preston would join her on stage. Frankly, it didn't sound like a joke. What's more, there's history ... the kid occasionally came out and danced on stage during her Femme Fatale tour.

In fact, during Britney's Circus tour back in 2009 ... K-Fed had beef with Brit over taking the kids on the road, but he settled it after getting $5k a week, as well as, all-expenses paid when he joined them on the road.