By MICHAEL GLYNN and ALAN SMITH

Vince Vaughn stormed out on girlfriend Jennifer Aniston after the former Friends star told him she was having second thoughts about their relationship, The National Enquirer can reveal.

Insiders say the two had a bitter late-night bust-up because Jennifer is determined to have a baby by the end of the year — but Vince doesn't want to start a family yet.

Now friends say the couple are heading for Splitsville. They met while filming an upcoming movie called, ironically, The Break-Up! "Vince is totally in love with Jen but he's not ready to start a family," said a pal.

"He's pushing for a commitment, but the bottom line is that Jen doesn't feel ready for an all-consuming relationship so soon after divorcing Brad Pitt."

For more, pick up this week's issue of The National Enquirer.