Sir Paul McCartney is taking legal action against Sony/ATV as he fights to reclaim ownership of the Beatles hits he wrote with John Lennon.
The musician filed a lawsuit in New York against the publishing firm - which controls the rights to songs including Love Me Do and All You Need Is Love - on Wednesday.
Sir Paul, 74, will soon be able to start reclaiming the rights under US copyright law - but court papers suggest he is worried about a legal challenge.
The papers state: "[The] Defendants have attempted to reserve their rights to challenge Paul McCartney's exercise of his termination rights on contractual ground.
It adds: "A judicial declaration is necessary and appropriate at this time so that Paul McCartney can rely on quiet, unclouded title to his rights."
The original rights to the songs - written by Lennon and McCartney between 1962 and 1971 - were sold to ATV Music in 1968 after the death of the Beatles' manager Brian Epstein.
The catalogue was famously bought in a $47.5m (£38.7m) deal by Michael Jackson in 1985 and later sold on to Sony/ATV following the star's death in 2009.
Sony/ATV told US magazine Rolling Stone it was "disappointed" by the lawsuit and described it as "both unnecessary and premature".
The publisher said: "Sony/ATV has the highest respect for Sir Paul McCartney with whom we have enjoyed a long and mutually rewarding relationship with respect to the treasured Lennon and McCartney song catalogue.
"We have collaborated closely with both Sir Paul and the late John Lennon's Estate for decades to protect, preserve and promote the catalogue's long-term value."
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