Aamer Madhani, and Kevin Johnson

USA TODAY

WASHINGTON -- The Justice Department is suing the city of Ferguson in an attempt to forcibly overhaul the city’s troubled police and court operations, Attorney General Loretta Lynch said Wednesday.

The decision comes hours after city leaders sought to revise a long- negotiated settlement, citing prohibitive costs of executing such a deal.

“There is no cost for constitutional policing,'' Lynch said late Wednesday.

"Painstaking negotiations lasted more than 26 weeks as we sought to remedy literally years of systematic deficiencies,'' she said of the government's action, which followed a public announcement last month of a tentative agreement that the attorney general described as "both fair and cost-effective . . . Last night, the City Council rejected the consent decree approved by their own negotiators; their decision leaves us no further choice.''

Lynch said the residents of Ferguson have been waiting "decades for justice,'' having endured civil rights breaches that established a pattern and practice of racially biased policing .

"I think the city of Ferguson had a real opportunity to step forward here,'' a visibly disappointed attorney general said. "Instead, they have chosen to step in the past.''

Earlier Wednesday, Ferguson Mayor James Knowles signaled that the city was ready to take on the Justice Department in federal court. He defended Ferguson's unanimous decision to revise the agreement by removing language from the agreement, which local leaders asserted, mandated big raises for police officers.

Local leaders also sought to free the city from its obligations under the agreement should Ferguson seek to shutter the police department altogether and enlist another agency to provide public safety services.

"The ball is in their court," Knowles said at a hastily called news conference in Ferguson. "We're sitting and waiting to talk. If they want to threaten legal action, then that's what they're threatening."

The threat became reality within hours of the mayor's appearance when the Justice lawsuit was filed in a Missouri federal court, alleging local law enforcement conduct routinely violated the Constitution.

"The residents of Ferguson have waited nearly a year for their city to adopt an agreement that would protect their rights and keep them safe,'' Lynch said. "They have waited nearly a year for their police department to accept rules that would ensure their constitutional rights and that thousands of other police departments follow every day.''

Justice Department threatens legal action against Ferguson

When Ferguson and Justice reached a tentative agreement last month, Knowles said the city did not then have a clear understanding of the cost of implementing it.

"I don't know if I'd characterize it as an absolute agreement in principle," Knowles said. "Also an agreement in principle doesn't allow you to assign a numerical value of every piece of the agreement."

The push to amend the deal comes after Knowles and council members raised concerns it could cost nearly $10 million over the next three years to implement.

The city of 21,000 has a budget of about $14 million and is facing about $2.8 million in debt after the August 2014 police shooting death of an unarmed black teenager, Michael Brown, sparked weeks of sustained and often violent protests. Much of the debt accrued from police overtime during the unrest following Brown's death and lost tax revenue from businesses destroyed or badly damaged in rioting.

A St. Louis County grand jury declined to indict Darren Wilson, the officer involved in the incident, and the Justice Department said it would not pursue federal civil rights charges against him. But the incident and subsequent protests led Justice to launch a wide-ranging investigation, concluding nearly a year ago that the city's police and municipal court unfairly targeted African-American residents, who make up about 70% of the population.

Ferguson's troubles and similar problems in cities across the country prompted a national discussion on police tactics and the appointment of a special White House panel, which in part urged the adoption of new strategies to rebuild a broken trust between law enforcement and the communities they serve.

In Ferguson, city leaders hosted a series of emotionally-charged hearings this month on whether it should ratify the tentative Justice settlement. Some residents urged the City Council to reject the deal and take their chances in court. Others favored the agreement as a way for the city to regain the trust of a wary African-American community.

Wesley Bell, a Ferguson council member, said members of the council felt it was important present their concerns about the costs of implementing the deal. He said the amendments to the agreement were not meant to be a "take it or leave it" offer.

"We hope the Justice Department is willing to sit down and talk to us and continue negotiations," Bell said. "If this case goes to court, it will not be because of the city of Ferguson."

Proponents of Justice agreement noted that fighting a legal battle would be costly and could prove more expensive in the long-term than settling now. Knowles disputed that notion Wednesday, saying the city's analysis shows "the agreement, as it currently stands, will cost more to implement than it would be to fight a lawsuit."

"Substantially more," Knowles added.