Federal prosecutors have sued New York City to speed reforms at the troubled Rikers Island jail complex.

The lawsuit was filed Thursday to address what a Justice Department investigation found was a culture of violence against young inmates.

It comes one day after Mayor Bill de Blasio visited Rikers to announce the end of solitary confinement for 16- and 17-year-old inmates. The end of solitary was just one of 73 recommendations made by federal prosecutors to curb the violence.

In court papers, Attorney General Eric Holder and Manhattan U.S. Attorney Preet Bharara (buh-RAH'-ruh) wrote that despite four months of negotiations with the city, federal prosecutors "have been unable to reach agreement as to lasting, verifiable and enforceable reforms."

Emails seeking comment from the mayor's office and city lawyers weren't immediately returned.