The request -- which has not yet been approved -- underscores the continuing concerns about security and the potential for violence at the Capitol, two months after rioters breached the building. It also comes as Capitol Police are increasing security after obtaining intelligence to suggest a "possible plot" by a militia group to breach the Capitol on Thursday.
"The United States Capitol Police Department is aware of and prepared for any potential threats towards members of Congress or towards the Capitol complex," the agency said in a statement Wednesday. "We have obtained intelligence that shows a possible plot to breach the Capitol by an identified militia group on Thursday, March 4."
The potential plot is tied to the far-right conspiracy theory promoted by QAnon supporters that former President Donald Trump will rise again to power on March 4, the original presidential inauguration day.
House Speaker Nancy Pelosi, D-Calif., responded to a question about the request for National Guard to stay the extra two months during her weekly press conference Thursday.
"The issue about the National Guard is one that will be made by the Capitol Police and the police board and the rest. But I'm not in a position to respond to that," Pelosi said. "But we should have them here as long as they are needed."
Pelosi rejected the notion that she was caving to the whims of domestic violent extremists after the House canceled Thursday votes amid the militia threat against the Capitol.
"I don't think anybody should take any encouragement that because some troublemakers might show up that we changed our whole schedule," Pelosi said. "No, we just moved it a few hours, and it largely will accommodate the Republicans going to their own session."
Defense officials confirmed that the request is under review at the Pentagon and that the Guard has started checking states for availability of troops, in an effort to be prepared if final Defense Department approval is given. The more than 5,000 Guard members currently in Washington, D.C., are all slated to go home on March 12, ending the current mission.
The Capitol Police said Wednesday that they "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."
Capitol Police said it is working with "local, state and federal partners to stop any threats to the Capitol."
"We are taking the intelligence seriously," Capitol Police said in a statement. "Due to the sensitive nature of this information we cannot provide additional details at this time."
The warning comes as law enforcement agencies around Washington, D.C., are increasing security.
Sources told Fox News on Wednesday that there is genuine concern surrounding activities on March 4, saying there is "specific stuff" from the "Three Percenters," a right-wing anti-government militia movement.
But sources told Fox News there is "no increase in hotel occupancy or flights" into D.C.
Moreover, there is "less detail" in this threat than in the now infamous Norfolk, Virginia, FBI bulletin the night before the Capitol riot, the sources say.
Meanwhile, members of Michigan’s National Guard have complained of receiving undercooked meals or food containing metal shavings during their stay in Washington, D.C., to protect the U.S. Capitol, according to news reports, as lawmakers from the state call for a new food provider. A National Guard spokesman on Wednesday acknowledged about 50 members have been treated for "gastrointestinal complaints" but said none were hospitalized.
U.S. Rep. Elissa Slotkin, D-Mich., said she learned that the request for a 60-day extension was made in the last 36 hours, and that the Guard is now seeking volunteers from states around the country to fill the need, The Associated Press also reported. She said some members of Congress have been concerned about whether there is a solid plan to provide security for members and staff going forward.
"We want to understand what the plan is," Slotkin said. "None of us like looking at the fencing, the gates, the uniformed presence around the Capitol. We can’t depend on the National Guard for our security."
Capitol Police acting Chief Yogananda Pittman testified before a House Appropriations subcommittee Wednesday that threats to members of Congress have increased by 93.5% within the first two months of 2021, compared to the same time period last year.
And from 2017 to 2020, Pittman said there has been a 118.66% increase in "total threats and directions of interests," with the overwhelming majority of suspects residing outside the National Capital Region (NCR) in Washington, D.C.
Slotkin said there has to be a plan that provides the needed security for the buildings and personnel by the Capitol Police and local law enforcement. Slotkin said it was telling that House members hastened to complete major votes Wednesday so they wouldn't have to be in the building where many fled violent rioters in January.
Lawmakers, she said, "don't feel totally secure" in the Capitol. Slotkin said, however, that she was going to her office to work on Thursday. "I'm not going to let these guys scare me away," she said.
Meanwhile, other sources told Fox News that Capitol security officials were leaving no stone unturned.
"They put out that statement to make sure nothing happens," said one source who asked they not be identified.
An additional source off Capitol Hill told Fox News they saw nothing in the regional intelligence to make them worried, but Fox News is told there is concern about a small contingent of insurrectionists coming to the Capitol perimeter.
"All it takes is a van full of people with weapons to mess with the National Guard," warned one source with familiarity of the Capitol security warning.
The FBI, in a statement to Fox News Wednesday, said: "While our standard practice is to not comment on specific intelligence products, the FBI is constantly gathering and sharing intelligence with our law enforcement partners."
"We are always on alert for any potential threats," the FBI said.
Earlier this week, in a memo to lawmakers, obtained by Fox News, Acting House Sergeant-at-Arms Timothy Blodgett on Monday said that officials are continuing to monitor "potential protests and activity surrounding what some have described as the ‘true Inauguration Day.’"
President Biden took office at noon on Jan. 20, as prescribed by the 20th Amendment, ratified in 1933.
The warning comes less than two months after pro-Trump rioters breached the U.S. Capitol on Jan. 6, during a joint session of Congress to certify the Electoral College results in favor of Biden. The Jan. 6 Capitol riot left five people dead, including a U.S. Capitol Police officer.
The House voted to impeach Trump on Jan. 13 for inciting insurrection — making him the first president in United States history to be impeached by the House of Representatives twice. Trump was acquitted by the Senate last month.
Meanwhile, after the riot, the Department of Homeland Security issued a National Terrorism Advisory System Bulletin after consulting with the intelligence community and federal law enforcement partners, warning that "there is currently a heightened threat environment across the United States that is likely to persist over the coming weeks."
The bulletin noted that the agency does not have any information to indicate any "specific" or "credible" plots, but cited violence and unrest across the country related to the presidential transition.
"DHS does not have any information to indicate a specific, credible plot; however, violent riots have continued in recent days and we remain concerned that individuals frustrated with the exercise of governmental authority and the presidential transition, as well as other perceived grievances and ideological causes fueled by false narratives, could continue to mobilize a broad range of ideologically-motivated actors to incite or commit violence," the bulletin read.
Fox News' Jason Donner and Dom Calicchio contributed to this report, as did The Associated Press.