Gwyneth Paltrow and Chris Martin reportedly agreed not to marry again until their children are adults.
The former couple - who have kids Apple, 11, and Moses, nine, together - split almost two years ago and it emerged last week the Coldplay frontman has yet to respond to divorce papers which he was served with in May last year.
It has now been claimed the Paradise hitmaker is deliberately "stalling" because he is concerned about how serious the Iron Man 3 actress' relationship with Brad Falchuk has gotten.
A source said: "The truth is, Chris stalling on signing documents is very much a calculated move to stop Gwyneth remarrying. He's just not ready to let her go.
"At the start, things with Brad and Gwyneth were very off and on but in recent months it's got serious and that hasn't gone unnoticed by Chris.