Music superstar Cher has sued the widow of her former husband and musical partner Sonny Bono over royalties for Sonny and Cher songs including I Got You Babe and The Beat Goes On.

In a federal lawsuit filed in Los Angeles on Wednesday (US time), Cher alleges that Mary Bono and other defendants have attempted to terminate provisions of business agreements Cher and Sonny Bono reached when they divorced in 1975 that entitled each to 50 per cent of songwriting and recording royalties.

The lawsuit says Sonny Bono’s heirs filed notice in 2016 they were terminating some of his song licensing agreements, but they “did not terminate, and could not have terminated” his agreements with Cher.

The breach-of-contract lawsuit alleges the damages to Cher are worth at least $US1 million ($A1.3 million).

Cher, the 75-year-old Grammy, Oscar and Emmy-winning singer and actress known for solo hits including Believe and film roles including Moonstruck, began performing as a duo with Sonny Bono in 1964. The two later had a TV variety show. They were married from 1967 to 1975.

Sonny Bono become mayor of Palm Springs and later a California congressman for the area. He died in a skiing accident in Lake Tahoe in 1998, and Mary Bono, his fourth wife, won his seat.

Mary Bono has not filed a response to the lawsuit. An email sent to a representative seeking comment was not immediately returned.