Washington DC - The National Guard is to stay on in Washington for another two and a half months, the Pentagon confirmed on Tuesday.

The US Secretary of Defense approved a request by Capitol Police for support from the National Guard to continue through May 23, Pentagon spokesman John Kirby said.

But the number of personnel is being reduced almost by half to 2,300.

Kirby said defense officials would work with Capitol Police to "incrementally reduce the National Guard footprint as conditions allow."

At the height of their mission, a total of 5,200 National Guard soldiers secured the Capitol. Their deployment was originally due to end on Friday.

Kirby said the decision to keep some of them on was made after a thorough review of the Capitol Police request and after close consideration of its potential impact on readiness.

The National Guard was called in to reinforce local security forces after supporters of then-President Donald Trump, who has since left office, stormed the Capitol on January 6 during a session of Congress and wreaked havoc.

The Capitol Police subsequently came under fire because security forces were not prepared for the attack and could not stop the intruders. Five people were killed, including a police officer.