CINCINNATI — An agreement aimed at reducing racial tensions unraveled a little more yesterday when the police union announced it was dropping out because of differences with the judge in charge.

The Fraternal Order of Police would be the second group to withdraw from the agreement, which followed three days of rioting in the city in April 2001.

Black activists got a federal judge’s permission to pull out on April 7. The Black United Front was unhappy with the pace of reforms, and wanted to focus on an economic boycott of the city that began after the rioting.

More than 200 police officers voted Monday night to drop out of the agreement, accusing U.S. District Judge Susan Dlott of being prejudiced against police.

The Fraternal Order of Police plans to ask Dlott, who is overseeing the agreement, to let it withdraw.

“We are the bastard stepchild of this whole agreement, and we are not going to put up with it anymore,” union President Roger Webster said.

A spokeswoman for Dlott declined to comment.

The riots began after a white police officer shot and killed Timothy Thomas, 19, a black man who was fleeing police on misdemeanor charges. A curfew ended the rioting after three days, and officer Stephen Roach was acquitted of charges in the shooting.

In the aftermath, the U.S. Department of Justice entered into an agreement with the city to make changes in the police department. The black activists and the police union were among the parties that approved.

Justice Department spokesman Jorge Martinez said yesterday that since the agreement was made between the department and the city, it would not be affected by the police union’s decision. But he said the department was disappointed that the deal had run into problems “as we believe that participation of all affected parties is the best way to affect change in this matter.”

The agreement combined the Justice Department’s deal with the city and the settlement of a lawsuit accusing the police department of harassing blacks. The union denied the lawsuit’s allegations, and the city also admitted no wrongdoing.

Under the settlement, the city agreed to create an independent agency to investigate complaints against the police and institute changes in police procedures.

Mayor Charles Luken has accused Dlott of bias because she ruled against the city three times in recent weeks in cases involving police.

One ruling involved a dispute over paying a former police monitor. She also agreed to let the activists’ lawyer stay involved in the agreement, even though the activists had withdrawn. She also allowed a lawsuit accusing police of excessive force to move forward.

Dlott was critical of the police department in her ruling allowing the Black United Front to withdraw.

“Unfortunately, such violations continue to occur despite the existence of the collaborative agreement,” Dlott wrote. “Inevitably, they will continue in the future.”

he police union cited her comments as the basis for pulling out.

“Judge Dlott will only harm community-police relations and cause more dissension and animosity if she continues with this farce,” said police union Vice President Keith Fangman.