BARRY MANILOW, 68, collapsed when he pushed the envelope after painful hip surgery, sources say.

The 68-year-old “Copacabana” singer’s legs buckled while he was rehearsing for his upcoming tour, and now friends fear he could end up confined to a wheelchair!

“Barry has been trying valiantly to prepare for this tour,” said a friend. “But his hips haven’t completely mended and he’s really been pushing it.

“Physical therapists were by his side on stage during rehearsals, but one time Barry tried to move without his walker and went down in a heap! He was in a lot of pain.”

The “Mandy” hitmaker underwent surgery on Dec. 12 to remove fluid and repair torn muscles in his hips. He was set to hit the road in support of his latest album “15 Minutes” when he collapsed during a recent rehearsal, the source said. Manilow wrote on his website: “We rehearsed for three weeks – me on my walker and in my wheelchair and my wonderful band, crew, lights, sound and nurses…We all had hopes that I’d be well enough to perform. But there’s just no way.”

He was forced to postpone gigs in New York City and Chicago, and with the tour now scheduled to start in Omaha on Feb. 29, friends fear he’s pushing himself too hard.

Barry’s body has broken down over the years. He was hospitalized for a heart scare in 2004 and was diagnosed with atrial fibrillation, an irregular and of­ten rapid heartbeat that can require emergency treat­ment.

“Barry is not a young­ster anymore, and he really needs to give him­self until at least the spring before his hips fully heal,” said his pal.

“If his hips break down completely, he could find himself forced to use a walk­er, or confined to a wheelchair – for good!”