The White House has expressed regret over its handling of domestic abuse allegations against a top aide.
Rob Porter, 40, quit on Wednesday as he denied two ex-wives' claims of physical and emotional abuse.
"We all could have done better over the last few hours, or last few days, in dealing with this situation," said deputy press secretary Raj Shah.
He told reporters Mr Porter, who was gatekeeper to the president, had been given an interim security clearance.
The White House staff secretary had yet to receive full security clearance because his background check was ongoing, said Mr Shah during Thursday's daily press briefing.
The president's chief of staff, John Kelly, is facing questions about when he knew of the allegations against Mr Porter.
The claims surfaced during FBI background check interviews with Mr Porter's ex-wives.
Mr Shah said the chief of staff only "became fully aware about these allegations" on Wednesday when photographs of an ex-wife with a black eye emerged.
Mr Kelly issued a statement late on Wednesday saying he was "shocked by the new allegations" against Mr Porter, referring to the black eye.
"There is no place for domestic violence in our society," he said.
Mr Kelly had previously defended Mr Porter as "a man of true integrity and honour".
US media report that Mr Kelly and other White House officials were aware for several months of the domestic abuse accusations because they were holding up Mr Porter's security clearance application.
Mr Shah said President Donald Trump "was surprised by it. He was disheartened by it. He was saddened by it."
"He, like many of us, did not see that in Rob Porter."
Announcing his resignation on Wednesday afternoon, Mr Porter said "these outrageous allegations are simply false".
"I have been transparent and truthful about these vile claims, but I will not further engage publicly with a co-ordinated smear campaign," he added.
His ex-wives, Colbie Holderness and Jennifer Willoughby, both recounted stories of his alleged misconduct.
His first spouse, Ms Holderness, said Mr Porter had kicked her on their 2003 honeymoon in the Canary Islands.
The US government analyst also alleged he punched her in the face while they were on holiday a couple of years later in Florence, Italy.
Ms Willoughby, a motivational speaker, told US media she was married to Mr Porter from 2009-13.
She wrote about her experiences in a blog post entitled Why I Stayed.
Ms Willoughby said she filed a protective order against him in June 2010 after he allegedly punched the glass of the door at their Alexandria, Virginia, home.
She told the Washington Post: "He has never faced repercussions that forced him to confront his issues."
A third woman who says she was Mr Porter's girlfriend contacted his ex-wives with allegations of "repeated abuse", according to CNN.
The unnamed woman was reportedly seeking advice on how to leave Mr Porter.
"I work in politics, and despite Rob's repeated abuse, some of which I think many know about, he continues to rise and I'm afraid to go against him," the woman reportedly wrote to Ms Holderness in 2016.
Mr Porter attended Harvard with President Trump's son-in-law, Jared Kushner, and was a Rhodes Scholar at Oxford University.
He formerly worked for Utah Senator Orrin Hatch, who said he was "heartbroken" by the allegations.
According to US media reports, Mr Porter has recently been romantically linked with White House communications director Hope Hicks.
She was reportedly involved in drafting the initial White House statement about Mr Porter on Tuesday.