The 74-year-old musician filed a lawsuit in New York in January (17), seeking a declaratory judgement that would pave the way for him to regain ownership of the songs he created as part of the band.

MCCartney is seeking to clarify the termination provisions of U.S. copyright law, which allows artists to reclaim the rights to songs recorded before 1964 after 56 years.

According to editors at Billboard magazine, on Monday (13Mar17) lawyers for Sony/ATV, who own the rights to the tracks, sent a letter to the presiding judge arguing that MCCartney's suit should be dismissed pending the result of a U.K. case with legal repercussions for proceedings.

The Beatles star's lawsuit followed a landmark decision at Britain's High Court in December (16) which went against the band Duran Duran, who were suing Sony affiliate Gloucester Place Music in a bid to renegotiate ownership of tracks from their own back catalogue.

Duran Duran's lawyers argued that agreements relating to the copyright of their music should be up for renegotiation after the 35 years stipulated by U.S. law, rather than protected for 70 years as British law dictates.

In the case, Mr Justice Arnold ruled that the provisions of British law supersede U.S. law, a judgement the Rio rockers are appealing.

If upheld, the ruling could scupper MCCartney's application to regain his own copyrights in October next year (18), 56 years on from The Beatles' first official recordings.

In the 1980s, the late Michael Jackson purchased the rights to several Beatles songs, including Hey Jude and Yesterday, and last year (16) his estate sold off the full rights of the tracks to Sony/ATV.

Lawyers for the music publishing giant argue that MCCartney's case should be dismissed pending the outcome of the U.K. case, and that a British court should decide which laws apply.

"Here, Plaintiff (MCCartney) is a U.K. citizen and the (copyright) Grants were negotiated and entered into in the U.K. with U.K. companies with respect to songs presumably written in the U.K. in return for payment in the U.K," Sony's lawyers write in their letter to the judge. "This Court would therefore presumably look to the Gloucester case, which is unsettled as it is currently being appealed."

The letter from Sony/ATV's lawyers came ahead of a conference where they are expected to file a motion seeking the dismissal of MCCartney's suit.