The U.S. Capitol Police are requesting for the extension of National Guard troops' assistance to help protect the complex, according to two officials.

The police officials' request comes due to fear of another assault and breaches on the U.S. Capitol by extremists. Concerns about the security of the building are still being raised months after the previous attack on Jan. 6.

The request was for a 60-day extension, with 5,000 troops in Washington slated to return home next week, according to an NBC News report.

Officials from the Defense Department said that the request was an initial one, with more details still to follow.

Defense officials are reported to be reviewing the proposal and there are negotiations between the Pentagon, while talks between the department, the police, and congressional authorities are ongoing.

Law enforcement was on high alert on Thursday around the Capitol after intelligence unraveled a possible plot by a militia group to breach in the building, according to an Associated Press report.

READ MORE: Capitol Rioter Says He's Following Trump's Orders, Apologizes to AOC for the Threat

Potential Security Threat

The possible threat was connected to the far-right conspiracy theory promoted by QAnon supporters, saying that former President Donald Trump would be on the top of the power once again on Mar. 4, which was the original presidential inauguration day.

There were no signs of any disturbing activities around the area on Thursday. However, the Capitol Police's request for the extension of the National Guard's assistance seemed delayed in confusion within authorities.

Rep. Elissa Slotkin said that she learned about the request in the last 36 hours. The National Guard is now looking for volunteers from states around the country to fill the request.

Memo from the Capitol Police to the congressional leader asks to keep up to 2,200 National Guard members in D.C. first, then reduce the number rationally based on the security threat.

Capitol police shall also deploy readily available technology and use mutual aid agreements to decrease the Guard footprint to a battalion-size as part of the plan. This would be around 900 soldiers as suggested by the Department of Defense on Feb. 22.

Republican Sen. Jim Inhofe said that the request is outrageous.

"That's not what they're supposed to be, that's not their mission. We have the Capitol Police, that is their mission," Inhofe was quoted in a report.

Before Capitol Riot

Former chief of Capitol Police Steven Sund said security officials at the House and Senate denied his early requests to call in the Guard members prior to the day of a demonstration in support of Trump, which then turned into a deadly attack on Congress.

Sund resigned from his post in January after House Speaker Nancy Pelosi called for his resignation, according to an NPR report.

He denied the claims of officials, saying that no one at the Capitol requested it. He said that House Sergeant-at-Arms Paul Irving was concerned with the optics of announcing an emergency prior to the protests.

The former Capitol Police chief added that he requested assistance six times before and during the attack on the Capitol. Sund said that those requests were denied or delayed.

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WATCH: Capitol Police request 2-month extension of National Guard at US Capitol - from WSPA 7News