Derek Chauvin, the white former Minneapolis police officer convicted of murdering African-American George Floyd, pleaded guilty Wednesday to federal civil rights violations charges in the crime, local media reported.

It was the first time that Chauvin, who is appealing his murder conviction in state court, admitted guilt for holding his knee to Floyd's neck for nearly 10 minutes until Floyd expired, in a case that sparked nationwide protests against police abuse of Black Americans.

Chauvin pleaded guilty to one federal charge of use of excessive force against Floyd, violating his constitutional rights, according to local Minnesota media at the federal courthouse in Minneapolis.

He also pleaded guilty to a similar charge against a juvenile in 2017.

Chauvin, who was sentenced in June to 22 and a half years in prison by a state judge for the murder of Floyd, faces a sentence of 20 to 25 years in the federal rights case.

That would be served concurrently with the sentence in the murder conviction.

His guilty plea ensures the 45-year-old former Minneapolis policeman will spend years in prison, whatever happens with his appeal on the murder charge.

Chauvin had originally pleaded innocent in the federal case. But the judge told him that if he had not changed that to guilty, he faced possible life imprisonment, according to local WCCO-TV.