WASHINGTON — The Defense Department took more than three hours to dispatch the National Guard to the deadly riot at the U.S. Capitol despite a frantic request for reinforcement from police, according to testimony Wednesday that added to the finger-pointing about the government response.

Maj. Gen. William Walker, commanding general of the District of Columbia National Guard, told senators that then-Capitol Police Chief Steven Sund requested military support in a 1:49 p.m. call, but the Defense Department's approval for that support was not relayed to him until 5:08 p.m. Guard troops who had been waiting on buses were then rushed to the Capitol.

That delay stood in contrast to the immediate approval for National Guard support granted in response to the civil unrest that roiled American cities last spring as an outgrowth of racial justice protests, Walker said. As local officials pleaded for help, Army officials raised concerns about the optics of a substantial National Guard presence at the Capitol, he said.

Walker told the joint hearing of the Senate Rules Committee and the Senate Homeland Security and Governmental Affairs Committee that Army Lt. Gens. Walter Piatt and Charles Flynn expressed to officials on the call that “it wouldn’t be in their best military advice to advise the secretary of the army not to have uniformed guard members at the capitol during the election confirmation.”

Flynn is the brother of Michael Flynn, who briefly served as national security adviser to former President Donald Trump, whose supporters stormed the Capitol.

Earlier in the hearing, Robert Salesses, acting assistant secretary of defense for homeland defense and global security, testified that Secretary of the Army Ryan McCarthy received approval from then-acting Defense Secretary Christopher Miller at 4:32 p.m. to deploy the D.C. National Guard to the Capitol, but Walker said he did not receive that authorization until 36 minutes later — and three hours and 19 minutes after Guard assistance was first requested by Capitol Police. The National Guard arrived at 5:20 p.m., Walker said.

“The response to the request took too long, so I think there needs to be a study done to make sure that never happens again,” Walker said. “It shouldn't take three hours to get a yes or no answer.”

Walker's account was consistent with the recollection of Robert Contee, the acting chief of the Metropolitan Police Department, who told senators at a separate hearing last week that he was “stunned” over the delayed response. Contee said Sund was pleading with Army officials to deploy National Guard troops as the rioting escalated.

Sen. Roy Blunt (R-MO) said during a break in the hearing that senators “certainly will have questions” for Miller and McCarthy.

“Whether that’s going to require testimony or not, I don’t know, but it’s definitely going to require an opportunity to ask them questions about their view, from their perspective, of why this decision-making process went so horribly wrong,” Blunt said.

Walker also testified that there was an “unusual” Pentagon memo on Jan. 5 that required him to seek advance authorization from Miller and McCarthy for specific measures during the pro-Trump gathering on Jan. 6.

The memo required Walker to seek personal authorization from the secretary of defense for equipment including weapons and body armor. Walker says the secretary of the Army separately authorized the use of protective equipment for the troops.

Walker told senators that if it had not been for the restrictions, he could have sent 155 members of the National Guard to the Capitol hours earlier.

“I believe that number could have made a difference,” Walker said. “We could have helped extend the perimeter and helped push back the crowd.”,

The Senate hearing was the latest about what went wrong on Jan. 6 as national security officials face questions about missed intelligence and botched efforts to quickly gather National Guard troops that day. The hearings have spelled out how police inadequately prepared for the Trump loyalists; that FBI warnings about the threat of violence did not reach top police officials; and that requests for aid were not promptly answered.

“We in the FBI want to bat 1.000, and we want to not have this ever happen again,” said Jill Sanborn, the bureau's top counterterrorism official and one of the witnesses. “So we're asking ourselves exactly the questions that you're asking: Is there a place we could have collected more [intelligence]? Is there something we could have done?”

Melissa Smislova, the acting undersecretary of the Department of Homeland Security for intelligence and analysis, told senators that “more should have been done” by the government “to understand the correlation between that information and the threat of violence, and what actions were warranted as a result.”

She said her office circulated 15 reports to law enforcement agencies before Jan. 6 warning of “the potential for domestic violent extremists  to mobilize quickly and attack large gatherings or government buildings.”

“I am deeply concerned that despite our best efforts they did not lead to an operational response to prepare and defend the U.S. Capitol,” Smislova said.

Meanwhile Wednesday, the Capitol Police disclosed the existence of intelligence of a “possible plot” by a militia group to breach the Capitol on Thursday. The revelation, coming as the acting police chief was testifying before a House subcommittee, differed from an earlier advisory from the House sergeant-at-arms that said Capitol Police had “no indication that groups will travel to Washington D.C. to protest or commit acts of violence.”

At a hearing last week, officials who were in charge of security at the Capitol blamed one another as well as federal law enforcement for their own lack of preparation as hundreds of rioters descended on the building, easily breached the security perimeter and eventually broke into the Capitol. Five people, including a Capitol Police officer, died as a result of the rioting.

Wednesday's hearing came as thousands of National Guard troops are still patrolling the fenced-in Capitol and as multiple committees across Congress are launching investigations into mistakes made on Jan. 6. The probes are largely focused on security missteps and the origins of the extremism that led hundreds of Trump supporters to break through the doors and windows of the Capitol, hunt for lawmakers and temporarily stop the counting of electoral votes.

Congress has, for now, abandoned any examination of Trump’s role in the attack after the Senate acquitted him last month of inciting the riot by telling the supporters that morning to “fight like hell” to overturn his defeat.

As the Senate heard from the federal officials, acting Capitol Police Chief Yogananda Pittman testified before a House panel that is also looking into how security failed. In a hearing last week before the same subcommittee, she conceded there were multiple levels of failures but denied that law enforcement failed to take seriously warnings of violence before the insurrection.

Pittman testified Wednesday that there has been a more than 93% increase in the number of threats received by members of Congress in the first two months of this year compared with the same period last year.

The Associated Press contributed to this report.