Usher could have quite a Mother's Day surprise for his mom, Jonetta Patton. The R&B superstar may be easing her out as his manager, according to insiders.

The muscle behind the putsch is said to be Usher's fiancee, Tameka Foster.

"They definitely don't get along," one spy tells us. "Tameka came to Jonetta's birthday on April 6. They hugged and posed for photos, but it was all for the cameras."

The rift dates back to when Jonetta encouraged Usher to fire Tameka as his stylist. "Tameka went on the radio and took some shots at Jonetta," says a source.

But Usher, 28, still liked Tameka, 38, and vice versa. In fact, she ended up leaving her husband for him. (Reps are denying she's pregnant.)

"Tameka has a hold over him," says one friend. "Nobody can figure it out. Some people think he may make Tameka his manager."

Execs at Jive, Usher's label, are said to be concerned. "They think Jonetta's done an incredible job with his career. They're encouraging her to take on Britney Spears."

A rep for Usher scoffed at talk that he's firing his mom: "I don't know of any management changes at this time."

Meanwhile, a source says Stuff editors are furious at Usher for "backing out" as host of the mag's Kentucky Derby party on Friday. "They originally wanted Justin Timberlake, but someone talked them into going with Usher," says the tipster. A Stuff staffer denies all of the above and says cover model Taryn Manning will host the bash.