ALBUQUERQUE, N.M. -- Boxer Johnny Tapia, a four-time world champion, says he's quitting the ring.

Tapia, 34, an Albuquerque native, was expected to fight for a fifth title this fall.

"I've had my last fight," Tapia told the Albuquerque Journal from his home in Las Vegas, Nev., in a copyright story published Wednesday. "I'm not going to fight again."

Alan Hopper of Don King Productions, Tapia's promoter, said from Miami that Tapia's decision was news to him, "and I don't think Don knows either."

A source close to Tapia told the Journal a formal announcement is expected by the end of the week.

Tapia recently signed with King and fought for him in June in Las Vegas, scoring a third-round knockout of Cesar Soto (53-9-3) of Juarez, Mexico.

Tapia's record is 50-2-2, the losses coming in decisions to Paulie Ayala in the last two years. Tapia felt he was cheated both times.

"I'm tired of everything ... that goes on outside the ring," he said. "I don't want to do it no more."

He has said several times since losing his last bout in June that he has lost interest in boxing.

Two years ago, after his first loss to Ayala, Tapia went into depression and was diagnosed with bipolar affective disorder. He was institutionalized twice.

Tapia turned pro in March 1988 after a successful amateur career that included stints with the U.S. National Team.

His first professional fight ended in a four-round draw, but he won his next 29 bouts -- 18 with knockouts -- before fighting to a draw again.

He tested positive for cocaine in October 1990 after beating Santiago Caballero at the New Mexico State Fairgrounds. For the next three years, he repeatedly failed drug tests.

With the help of his wife and trainer, Teresa Tapia, he began testing clean in 1994 and returned to boxing on March 27, 1994.

Tapia won the WBO junior bantamweight title in October 1994, and defended it nine times.

The biggest fight of his career came in July 1997, when he scored a unanimous decision over hometown rival Danny Romero to win the IBF junior bantamweight title.

He moved up to bantamweight and won the WBA title in December 1998. He lost that belt to Ayala in their first fight.

He won the WBO bantamweight title in January 2000 but vacated it when he decided last year to move up in weight class.