Attorney General Jeff Sessions on Friday dispatched five additional prosecutors to Chicago as the Justice Department filed a brief opposing a pending consent decree that will reform the nation’s third-largest police department.

The new prosecutors would work with state and city prosecutors to speed up the arrest and prosecution of Chicago’s most violent criminals, the Justice Department said in a news release.

The action comes on the same day Mr. Sessions filed a brief opposing a consent decree between the Chicago Police Department and the State of Illinois.

Matt McGrath, a spokesperson for Mayor Rahm Emanuel said the new prosecutors are welcome, but derided the consent decree opposition.

“We’ll definitely appreciate additional resources to hold gun offenders accountable, but we don’t appreciate efforts - even a half-hearted one like this legal brief - to impede our public safety reforms or inhibit our efforts to rebuild the bonds of trust between officers and residents,” Mr. McGath said in a statement.

Mr. Sessions said the agreement will undercut police efforts to curb gun violence in Chicago. The pact would reduce the use of force among officers and increase oversight by having a federal judge monitor the police. Other reforms in the consent decree would require officers to document each they draw a weapon.

A federal judge is set to decide on the consent decree later this month. The Justice Department action comes ahead of a Friday deadline for written comment on the pact.

“There is one government institution and one alone that has the ability to make Chicago safer — that is the Chicago Police Department,” Mr. Sessions said in a statement Friday. “Our goal should be to empower it to fulfill its duties not to restrict its proper functioning or excessively demean the entire Department for the errors of a few.”

“Make no mistake: unjustified restrictions on proper policing and disrespect for our officers directly led to this tragic murder surge in Chicago,” he said.

The Illinois State Attorney General and Mayor Emanuel pushed for the consent decree after an Obama-era Justice Department probe accused the Chicago police of racially discriminatory tactics.

President Trump and Mayor Emanuel continue to bicker over issues like stop and frisk policing and Chicago’s status as a sanctuary city.

In addition to the new prosecutors and consent decree challenge, U.S. Attorney John Lausch will create a gun crimes prosecution team that will focus on cases emerging from Chicago’s most violent neighborhoods.

The Bureau of Alcohol, Tobacco, Firearms and Explosives will also assign five violent crime coordinators to the city.

The additional manpower will supplement the Chicago Crime Gun Strike Force, a team of 21 ATF agents and 12 Chicago police officers, created by Mr. Sessions in June 2017.