Washington DC - The Justice Department reached an agreement on Friday with Washington authorities over control of the US capital's police department after President Donald Trump placed it under federal government control to tackle violent crime.

The deal was hammered out at a federal court hearing held after the District's attorney general sued the Trump administration over what he called a "hostile takeover" of the city's police force.

Trump placed Washington's Metropolitan Police Department (MPD) under federal control on Monday and ordered the deployment of 800 National Guard troops onto the streets of the capital.

Trump's attorney general, Pam Bondi, then issued an order on Thursday to install a hand-picked official – Drug Enforcement Administration (DEA) chief Terry Cole – as "emergency" police commissioner.

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Brian Schwalb, the attorney general for Washington, responded with a lawsuit arguing that federal law governing the capital "does not authorize this brazen usurpation of the District's authority."

At the court hearing on Friday, District Judge Ana Reyes urged the two sides to work out a solution, and they agreed that Cole, rather than assuming direct control of the MPD, would give directives through the mayor's office.

"Mr. Cole is not going to be able to direct police department individuals to do anything," Reyes said. "He's going to have to go through the mayor."

Schwalb welcomed the agreement at a press conference following the court hearing.

"My expectation is that the key issue with respect to control and command of our MPD has been resolved today, and that it is clear as a matter of law that it is under the chief of police appointed by the mayor," he said.

"We don't need a hostile takeover from the federal government to do what we do every day," he said.