LOS ANGELES — Rock 'n' roll veteran John Phillips, the founder and main songwriter for the 1960's California pop group the Mamas and the Papas, died of heart failure Sunday morning, his spokeswoman said. He was 65.

Phillips, who received a liver transplant several years ago after years of drug and alcohol abuse, died at UCLA Medical Center at 8:15 a.m. PST, surrounded by family and friends, spokeswoman Elizabeth Freund said.

Although the Mamas and Papas lasted for just three years until 1968, the quartet recorded some of the most memorable tunes of the pop era, including "California Dreamin'," "Monday, Monday" and "Creeque Alley."

The group also included Phillips' wife, Michelle (they divorced in 1970), Denny Doherty and "Mama" Cass Elliot, who died in 1974. The survivors reunited in 1998 to sing "California Dreamin' " at the group's induction into the Rock and Roll Hall of Fame.

Phillips also helped organize the 1967 Monterey Pop Festival, which introduced artists such as guitarist Jimi Hendrix and English rock band the Who to American audiences.

Additionally, he wrote or co-wrote songs for other artists, including "San Francisco (Be Sure To Wear Flowers in Your Hair)" for Scott McKenzie in 1967; "Kokomo," a No. 1 hit in 1988 for the Beach Boys; and "Me and My Uncle" for the Grateful Dead.

Freund told Reuters that Phillips had been in the hospital for several weeks. He had been in great pain after falling off a stool and badly hurting his shoulder. But the pain turned out to be related to a stomach virus that affected his kidneys.

Doctors were anticipating putting him on dialysis and transferring him to an occupational therapy center in Palm Springs, east of Los Angeles, when Phillips took a turn for the worse in the past few days.

"His liver was doing OK," Freund said. Some tabloid reports had suggested recently that Phillips was waiting for another liver. His friend and producer Harvey Goldberg said Phillips had been sober for many years. Phillips had also undergone two hip replacements in recent years.

He was born in Parris Island, S.C., on Aug. 30, 1935. After stints at George Washington University and the U.S. Naval Academy, he became active in the New York folk community in the mid 1950s.

He formed a group called the Journeymen, whose lineup included southern California native Michelle Phillips, who had come east to be a model. They married in 1962. Canadian native Denny Doherty later joined the group, by then known as the New Journeymen.

The Mamas and the Papas took form in 1965 when Doherty's former Mugwumps bandmate, Cass Elliot, joined the trio, which had relocated to California. The group's convoluted beginnings are recounted in the autobiographical song "Creeque Alley," a No. 5 hit in 1967.

In all, the group had six top five hits in 1966 and 1967. "Monday, Monday" was No. 1 for three weeks in 1966. Although they were hippies, they stayed credible at a time when rock 'n' roll was becoming politicized. Their sumptuous folk-pop harmonies were a lasting tribute to Phillips' songwriting, arranging and producing skills.

"There was a sophistication to the style of the melody and lyrics he wrote that almost approaches poetry," said Goldberg.

After four studio albums, the group disbanded in 1968. Phillips made a solo LP "The Wolf King of L.A.," split with his wife and was involved in a legal tangle with his former bandmates and their Dunhill label. They reunited briefly in 1971 to record the little-appreciated album "People Like Us."

During the 1970s, Phillips and new wife Genevieve Waite were sidetracked by big drug habits. In 1980, strung out on heroin and cocaine, he was arrested for drug trafficking and spent a month in jail after being convicted of a lesser charge.

As often happens with rockers on the rebound, Phillips was on a strong creative streak at the time of his death, according to Goldberg. Phillips had just completed an album of new material, tentatively titled "Slow Starter," which included an update of "California Dreamin'." His collaborators on the album included "Late Show" bandleader Paul Shaffer and British rock guitarist Chris Spedding, said Goldberg.

He had also completed a record he started over 25 years ago with Mick Jagger and Keith Richards of the Rolling Stones, entitled "Pay Pack and Follow", which is set for release in May via U.K. label Eagle Records, Goldberg said.

A movie about the band started development at Twentieth Century Fox last year, with cooperation from the group's surviving members and the Elliot estate.

Phillips is survived by his wife Farnaz; daughters MacKenzie, an actress best known for her work on the TV sitcom "One Day At A Time"; Chynna, a member of celebrity offspring trio Wilson Phillips; Bijou, a pop singer; sons Jeffrey and Tamerlane; step-daughters Atoosa and Sanaz. No funeral or memorial arrangements have been made yet.