The U.S. Capitol Police have requested a 60-day extension of some of the 5,200 National Guard members activated in the District in response to security threats and the Jan. 6 assault on Congress, opening the door to a military presence in the nation’s capital into spring, defense officials said Thursday.

Acting chief Yogananda Pittman submitted the request to the Defense Department for an extension, the Capitol Police said in a statement on Thursday evening, without saying for how long.

“The USCP is extremely grateful for the Department of Defense and the National Guard support provided since January 6th,” the statement said. “We understand the Guard has a tremendous service need back home responding to the COVID-19 pandemic.”

Three defense officials said that the Pentagon received the extension request and that Defense Secretary Lloyd Austin and Army officials will consider it. If approved, it would keep Guard members on duty through May, said the officials, who spoke on the condition of anonymity because of the sensitivity of the issue.

A senior defense official said Thursday night that the department had just received the request. The official declined to characterize it, saying it would premature to speak about it.

About 5,200 Guard troops are on duty in Washington now, staffing a security perimeter around the Capitol that includes miles of fencing around one of the major symbols of American democracy. It was installed after the Jan. 6 insurrection, launched by supporters of President Donald Trump after a rally in support of his false claims that he won the election.

House Speaker Nancy Pelosi (D-Calif.) was noncommittal when asked on March 4 about a report that the National Guard may guard Congress for two more months. (The Washington Post)

The D.C. National Guard referred questions about the request, first reported by the Associated Press, to the Pentagon.

“The current mission extends to March 12,” said Capt. Edwin Nieves, a spokesman for the D.C. National Guard. “We do not have an authorized extension of that mission at this time.”

The request appeared to catch D.C. Mayor Muriel E. Bowser (D) by surprise.

“It was our expectation that the additional forces would be leaving now,” she said, adding that the Capitol Police have had limited communication with the city about their security requests. “We don’t know why additional forces have been requested until May. … It was our expectation that the National Guard support would be lessened significantly around this time.”

The request comes after Capitol Police officials said Wednesday that they had information about a possible attempt by a militant group to breach the Capitol on Thursday, a date that some followers of the QAnon extremist ideology falsely claim will mark Trump’s return to the White House. The House canceled a session on Thursday in response, while the Senate remained in session to consider President Biden’s $1.9 trillion coronavirus relief package.

“We have already made significant security upgrades to include establishing a physical structure and increasing manpower to ensure the protection of Congress, the public and our police officers,” the Capitol Police said in a statement Wednesday.

Concerns about QAnon at the Capitol were not borne out Thursday. Guard members remained on duty, with the fencing and barbed wire still in place, but there was no violence.

Rumors of the National Guard extending its stay in Washington have persisted for weeks. One defense official familiar with the talks said that discussions have included the possibility of scaling back the number of troops around the Capitol but keeping others ready at the D.C. Armory, about two miles away, in case of emergency.

The National Guard initially responded a few hours after the breach of Congress, in a move that critics have said was too slow. Its presence expanded to about 26,000 members from across the country for Biden’s inauguration on Jan. 20 and has steadily declined since.

The entire D.C. National Guard has about 2,700 soldiers and airmen, according to Guard officials. About 1,100 of them are devoted to the Capitol security mission, Nieves said.

They are supplemented by Guard members from multiple states, who are sent at the direction of their governors. While in the District, they are all under the command of Maj. Gen. William Walker, the head of the D.C. National Guard.

The appearance of the military forces, and the onerous security measures in place, has become controversial — and politicized — in recent weeks.

On Thursday, Sen. James M. Inhofe (Okla.), the ranking Republican on the Senate Armed Services Committee, called the request “outrageous.”

Inhofe said the extended deployment of National Guard members, who mostly have civilian jobs, is destroying people’s careers.

“That’s not what they’re supposed to be. That’s not their mission,” Inhofe said. “We have the Capitol Police. That is their mission. And we don’t — so I can’t think of any stronger terms to tell you.”

Sen. Amy Klobuchar (D-Minn.), the chairwoman of the Senate Rules and Administration Committee, said she would like to see the number of Guard members “eventually” curtailed.

“But you want to listen to the law enforcement intelligence about what is safe,” she said. “But look at what that is.”

Rep. Peter Meijer (R-Mich.), whose state has Guard members in the District, expressed frustration with a lack of transparency by the Capitol Police.

“Getting information from Capitol Police leadership has been like pulling teeth,” he tweeted. “Direct answers are hard to come by — I learn more from what’s leaked to media than in briefings. We cannot allow the National Guard to be used as a bandaid for a lack of USCP strategy/leadership.”

Rep. Elissa Slotkin (D-Mich.) said in a statement Thursday that she was hearing from National Guard officials about the Capitol Police request for an extension and that the National Guard is soliciting states to send or keep forces in the District. She also called for more transparency.

“No one likes seeing the fortress-like security around the Capitol. And no one wants to again have a security problem in and around this symbolic place,” she said. “But whether an extension has been requested or the mission is indeed terminating on March 12, it’s critical that members of Congress get a briefing on what’s behind these decisions.”

Sen. Roy Blunt (Mo.), the ranking Republican on the Senate Rules and Administration Committee, said that the panel hadn’t been briefed on the extension plans but that “some active military police guard in a more permanent basis near the Capitol could be a good idea in the foreseeable future.”

“Principally because they’d actually be able to relieve the Capitol Police from some of their duties, which have been overtime and all time for longer than it should have been,” he said. “So I’m thinking about that for one option.”

But some Republicans have questioned the need for the National Guard to stay since the inauguration.

In a letter to acting Army secretary John E. Whitley in late January, a group of Republican lawmakers said National Guard members are deployed on short notice, pulled away from their families and jobs, and have endured “unprecedented stress on the force” after a year in which they responded to the coronavirus pandemic, social unrest, natural disasters and continuing deployments overseas.

“The National Guard should be used as an option of absolute last resort,” they wrote. “We are seeking clarification and justification on behalf of the National Guard men and women that have kept us safe over the past month and year.”

Whitley referred their questions in a letter last month to the Capitol Police.

At least one of the lawmakers, Rep. Michael Waltz (R-Fla.), later spoke with Whitley, said a congressional official, who spoke on the condition of anonymity because of the sensitivity of the issue.

“We’ve continued to press for more information regarding specific threat levels and have yet to receive any in-depth briefs,” Waltz said in a statement. “If threats are serious enough to justify keeping thousands of National Guard soldiers away from their families and full-time jobs rather than relying on Capitol Police to handle, we need to know about it.”

Julie Zauzmer, Paul Kane, Alex Horton and Marianna Sotomayor contributed to this report.