LOS ANGELES (CNS) — Cher has lost her rights to receive royalties from such 1960s Sonny & Cher hits as "I Got You Babe" and "The Beat Goes On," the widow of former Palm Springs Mayor Sonny Bono argues in new court papers obtained Thursday.

Mary Bono is asking a federal judge to dismiss a $1 million lawsuit brought by Cher last year that alleges the former U.S. representative is unfairly withholding royalties from songs made famous with the singer-actress' ex-husband.

The 75-year-old entertainer claims that Bono's fourth wife and widow waived provisions that entitle Cher to 50% ownership of the duo's musical composition royalties, record royalties and other assets.

In documents filed Wednesday in support of dismissal, Mary Bono contends that the Copyright Act allows Sonny Bono's widow and children to reclaim Sonny Bono's copyrights from publishers.

A hearing to discuss the pending motion is set in Los Angeles federal court for April 11.

According to the lawsuit, after Cher and Sonny Bono divorced in 1975, they agreed to split revenue from the songs recorded together. Attorneys for Cher allege that in recent years, Sonny's widow has "undone" Cher's ownership of those rights and royalties.

Attempts to reach Mary Bono were not immediately successful.

Cher and Sonny Bono married in 1964 and began performing under the name Caesar and Cleo before switching to Sonny & Cher. In addition to their music, the couple built their celebrity via television, starring in the 1971-74 CBS variety show, "The Sonny & Cher Comedy Hour."

Their career as a duo waned by the mid-1970s, though each was successful on their own — Cher in movies such as "Mask" and "Moonstruck" and Bono as a California politician.

Sonny Bono was mayor of Palm Springs from 1988-92 and a Republican congressman from 1995 until his death in a skiing accident in 1998. He was succeeded by Mary Bono, who served until 2013.