US Capitol Police and security officials want a renewed emergency declaration to extend the National Guard presence at the Capitol possibly into May, a source said.
About 5,000 National Guard troops still in Washington since the January 6 riot at the Capitol are set to return home by March 12, and a new emergency declaration would have them stay for another two months, the source said.
The exact size of the presence during that time could change, but some will probably stay to allow for a quick response if needed.
The Capitol Police are required to make a formal request to the National Guard Bureau for an extension of the troops’ presence.
Tension heightened this week amid warnings of another planned attack on the Capitol on Thursday by a right-wing militia group, but by midday that had not occurred.
Nevertheless, the House cancelled plans for votes and other events late on Wednesday after the threat, which was described in alerts from the FBI, Homeland Security and Capitol Police.
The Senate remained in session.
Law enforcement officials from federal agencies say there are continuing security threats to the Capitol building and politicians.
A barrier of fencing and razor wire was placed around the Capitol after a mob of former president Donald Trump’s supporters stormed the building.
Robert Salesses, an acting assistant defence secretary, told two Senate committees on Wednesday that military officials did not yet know how long National Guard troops would stay at the Capitol.
Mr Salesses said a meeting was planned for next week on the subject.
On Thursday, House Speaker Nancy Pelosi said such decisions were up to security officials.
But Ms Pelosi said there was now a draft report of an initial security review led by retired Lt Gen Russel Honore of Capitol Complex security after the January assault.
National Guard spokeswoman Darla Torres said there was no decision on extension requests and that approval would come from the Secretary of Defence, Lloyd Austin.