U.S. Attorney General Jeff Sessions is asking for the resignations of 46 United States attorneys who were appointed during prior presidential administrations, the Justice Department said Friday.

Many of the federal prosecutors who were nominated by former president Barack Obama have already left their positions, but the 46 who have remained in the first weeks of the Trump administration have been asked to leave “in order to ensure a uniform transition,” Justice Department spokeswoman Sarah Isgur Flores said in a statement e-mailed to USA TODAY.

“Until the new U.S. attorneys are confirmed, the dedicated career prosecutors in our U.S. attorney’s offices will continue the great work of the department in investigating, prosecuting and deterring the most violent offenders,” she said in the statement.

In another statement e-mailed to USA TODAY, Justice Department spokesman Peter Carr said President Trump telephoned U.S. attorneys Dana Boente of the Eastern District of Virginia and Rod Rosenstein to say "that he has declined to accept their resignation, and they will remain in their current positions."

Boente is the acting deputy U.S. attorney general, appointed by Trump to replace Sally Yates, who was dismissed by Trump after she refused to defend his travel ban. Rosenstein is U.S. attorney for the district of Maryland. He was nominated under the younger President Bush.

One of those who has resigned is U.S. Attorney Andrew Luger, who represented the state of Minnesota and was nominated in 2013 under President Obama.

"At the request of the Attorney General of the United States, I have submitted my resignation to the President, effective immediately," Luger said in a statement released Friday.

Peter F. Neronha, the U.S. attorney for Rhode Island, also announced his resignation Friday.

Preet Bharara, the U.S. attorney for Manhattan known for pursuing dozens of insider trading cases, was among those asked to leave. In November, the Wall Street Journal reported that Bharara had agreed to stay in his current role under Trump.

U.S. Sen. Charles Schumer, D-N.Y., wrote on Facebook that he was "troubled" to learn of the request for Bharara to step down "after the President initiated a call to me in November and assured me he wanted Mr. Bharara to continue to serve as U.S. Attorney for the Southern District."

"By asking for the immediate resignation of every remaining U.S. Attorney before their replacements have been confirmed or even nominated, the President is interrupting ongoing cases and investigations and hindering the administration of justice," Schumer wrote.

Sen. Dianne Feinstein of California, the senior Democrat on the Senate Judiciary Committee, told The Associated Press Friday that she was surprised by Sessions' action.

"Under previous administrations, orderly transitions allowed U.S. attorneys to leave gradually as their replacements were chosen," the senator said in a statement. "This was done to protect the independence of our prosecutors and avoid disrupting ongoing federal cases."

The independence of federal prosecutors is especially important now that Sessions has recused himself from any investigation into the Trump campaign's ties to Russia, Feinstein said.

"That’s why many of us have called for the appointment of a special prosecutor," she said.

She said she met with White House Counsel Donald McGahn in January and was told "that the transition would be done in an orderly fashion to preserve continuity."

"Clearly this is not the case," Feinstein said. "I’m very concerned about the effect of this sudden and unexpected decision on federal law enforcement."

It is customary for the country’s 93 U.S. attorneys to leave their positions once a new president is in office, but the departures are not automatic. One U.S. attorney appointed by President George W. Bush -- namely, Rosenstein -- remained on the job for the entire Obama administration and is the current nominee for deputy attorney general.