Baltimore's mayor and police chief worked closely with Justice Department investigators to scrutinize the city's police force and embraced a plan they crafted to overhaul the troubled department.

So they were surprised by the Justice Department's sudden request Monday for more time to see how the proposed changes might conflict with the aggressive crime-fighting approach new Attorney General Jeff Sessions favors.

City leaders accelerated negotiations under the Obama administration to get the consent decree done before the change in administrations in Washington "because we know that a consent decree will make the Baltimore police department better both with crime fight and community relationships," Police Commissioner Kevin Davis said Tuesday.

A consent decree binds the police commissioner and mayor, no matter who they are, "to getting those reforms enacted under a timeline that's not necessarily our own," he said. The department is already enacting reforms, Davis said, but change won't come at the pace that it is needed without such an agreement.

"The reforms that cost money ... are the things behind the scenes that consent decrees really mandate and they hold our feet to the fire," he said.

Davis and Democratic Mayor Catherine Pugh believed the proposed agreement would repair public trust in the police while also quelling violence. They swiftly voiced their opposition to the requested delay, and pledged to press ahead with the business of transforming the police department, with or without a court-enforceable consent decree.

"Much has been done to begin the process of building faith between the police department and the community it seeks to serve," Pugh said in a statement. "Any interruption in moving forward may have the effect or eroding the trust that we are working hard to establish."

Interim City Solicitor David Ralph wouldn't say whether the city will file in opposition to the federal motion, but said such a filing would be made public. He said the motion came days after he discussed the upcoming hearing with Justice Department lawyers.

"What's changed?" Ralph asked. "I can only take what they've said in the motion at face value."

Pugh said Tuesday that the city has already begun the reforms, but needs more money and support from the federal government to complete the process. She says the city has set aside some money for improvements, and while it's "not nearly enough," it's "enough to get things moving."

The government's request for a 90-day continuance came three days before a scheduled hearing before a federal judge, and just hours after Sessions announced he had ordered a sweeping review of the Justice Department's interactions with local law enforcement, including existing or proposed consent decrees.

It provided an early glimpse of the attorney general's stance on police department oversight and his ambivalence about mandating widespread change of local law enforcement agencies.

Sessions, an Alabama Republican who cultivated a tough-on-crime reputation during 20 years in the Senate, has repeatedly expressed concern that lengthy investigations of a police department can malign an entire agency. That view reflects a dramatic break from President Barack Obama's administration, which saw such probes as essential in holding local law enforcement accountable for unconstitutional practices.

Vanita Gupta, head of the Civil Rights Division under Obama, said the request "is alarming and signals a retreat from the Justice Department's commitment to civil rights and public safety in Baltimore," especially because the agreement sought the input of community members, police union officials and department heads to "address serious constitutional violations that had undermined trust and public safety in the city."

The federal government cited several reasons for the requested delay, including new Justice Department policies that federal officials say are aimed at reducing crime.

If granted, the request would effectively stall a process that could lead to a sweeping overhaul in the policies and practices of the Baltimore police force. The two sides reached agreement on a consent decree earlier this year before Attorney General Loretta Lynch left the Justice Department.

The department said it was aware of the need for police reform in Baltimore but added that the city "has made progress toward reform on its own and, as a consequence, it may be possible to take these changes into account where appropriate to ensure future compliance while protecting public safety."

In addition to Baltimore, the review also renewed questions about the fate of negotiations with Chicago's police department after a report released in the final days of Lynch's tenure found officers there had violated the constitutional rights of residents for years.

Sessions has not committed to such an agreement and has repeatedly said he believes broad investigations of police departments risk unfairly smearing entire agencies and harming officer morale. He has also suggested that officers' reluctance to aggressively police has contributed to a spike in violence in some cities.

The proposed consent decree in Baltimore comes after the Justice Department released a scathing report detailing longstanding patterns racial profiling and excessive force within the city's police force. The review was prompted by the death of Freddie Gray, a 25-year-old black man whose neck was broken in the back of a transport wagon, and whose death roiled the city.

Activist Ray Kelly said the requested delay undermined hard-fought efforts to heal the fractured relationship.

Kristen Clarke, president and executive director of the Lawyers' Committee for Civil Rights Under Law, initially voiced concern after the Justice Department asked for a delay of court proceedings earlier this year. On Monday, she called the Justice Department's request "deeply concerning."

"The residents of Baltimore have waited a long time for relief, and the Justice Department provided a roadmap, setting forth in great detail the systemic problems that riddle the police department," she said. "That the Justice Department will turn its back on issues so dark and severe is deeply disturbing."