WASHINGTON >> Officials in Ferguson, Mo., have reached the outlines of a deal with the Justice Department that would force changes to the city’s Police Department and head off a civil rights lawsuit alleging years of unconstitutional policing, local and federal officials said.

Completing the deal, however, will require support from diverse factions of Ferguson’s leadership, which will have to sell residents on the idea of a federal policing monitor and of huge new expenses for a city that is already struggling financially. Some officials said a local tax increase appears unavoidable, which in Missouri requires approval from voters.

The agreement, which would be filed in federal court, would require new training for police officers and improved record-keeping, and would install a federal monitor to ensure those changes were made, officials said.

The two sides have been negotiating for several months, after a scathing Justice Department report in March described Ferguson as a city where police officers often stop and arrest people without cause, where the court operates as a moneymaking venture, and where officers used excessive force almost exclusively against blacks.

The deadly police shooting of Michael Brown, a black teenager, in August 2014 led to protests in Ferguson and plunged the nation into a tumultuous debate over race, policing and the use of force. Fatal police encounters in Cleveland, Baltimore, New York and Chicago also fueled unrest, but it was Ferguson, a city of 21,000, that became shorthand for controversial policing.

“We have made tremendous progress. We’re very close,” Mayor James Knowles III said in a telephone interview. He said “small sticking points” remained, although he declined to describe those points or to provide details of items being negotiated.

“We’re at a point where we have addressed any necessary issues, and assuming it is not cost prohibitive, we would like to move forward,” Knowles said.

Separately, federal officials confirmed that they had reached the outlines of a deal and that they were optimistic it would be completed soon. They spoke on the condition of anonymity because they were not authorized to discuss the matter.

“The talks with the city of Ferguson to develop a monitored consent decree have been productive,” Dena Iverson, a spokeswoman for the Justice Department, said in a statement. “The department believes that in order to remedy the Justice Department’s findings, an agreement needs to be reached without delay.”

In its March report, the Justice Department highlighted the need for training, saying that officers appeared not to know one of the fundamentals of policing, that arrests can be made only with probable cause. Federal investigators said Ferguson police officers also used a system of so-called ped checks to stop pedestrians without probable cause and demand to see their identification.

The agreement is also expected to force changes to the municipal court system, which the Justice Department said trapped people in a cycle of increasing fines and arrests, even for routine violations. It is highly unusual for the Justice Department to demand changes to a court, but Ferguson is unique in that its court system operates as an arm of the Police Department, not as an independent branch of government, according to the federal report. It is not clear what changes the city has agreed to make to that system.

While some city leaders have disagreed with elements of the Justice Department’s findings, Knowles said he was eager to reach a settlement and was hopeful that he would have the votes he needed from the six members of the City Council. A settlement would remove the immediate threat of a long and expensive court fight, which could end with a judge forcing the city to make changes anyway.

“To me, fighting that at this point does what?” Knowles said of the Justice Department report. “The idea that we want to spend millions to fight something when we could spend half a million, or whatever, on equipment and training? That’s what we have to do.”