The Department of Defense's press secretary apologized Monday for not being more transparent about information regarding Defense Secretary Lloyd Austin's recent hospitalization -- which the White House learned about three days after he was hospitalized for complications resulting from what was characterized as "a minor, elective procedure."
Austin had an elective procedure on Dec. 22 and then went home the next day; however, on Jan. 1, "he began experiencing severe pain and was transported" back to Walter Reed National Military Medical Center in Bethesda, Maryland, said Maj. Gen. Pat Ryder, the Department of Defense press secretary.
Ryder said he was informed about Austin's hospitalization on Tuesday, Jan. 2. The White House learned about it on Thursday night; Congress was first notified hospitalization on Friday afternoon -- shortly before it was made public in a Pentagon news release.
MORE: Lloyd Austin was hospitalized after 'experiencing severe pain,' Pentagon says"I recognized that I should have tried to learn more, and to press for an earlier public acknowledgement," Ryder said Monday to the Pentagon press corps. "So I want to offer my apologies and my pledge to learn from this experience. And I will do everything I can to meet the standard that you expect from us."
Ryder knew of Austin's hospitalization when he went to the podium on Thursday afternoon for an on-camera briefing -- but said he had not followed up on Austin's condition.
On Tuesday, Austin's Chief of Staff Kelly Magsamen was sick with the flu, but she was made aware of his hospitalization, as was Austin's senior military aide, Ryder said. However, Magsamen's illness caused a delay in the notifications, he added.
"We are currently reviewing how we can approve these notification procedures to include White House and congressional notifications," Ryder said.
Ryder offered additional details about which of the country's top defense officials knew what and when.
Deputy Defense Secretary Kathleen Hicks was made aware of Austin's hospitalization on Thursday, Ryder said. She worked with Magsamen on a plan to notify the White House and Congress as well as issue a press statement, he added. It appears it took them almost a full day to contact Congress and work up a press release that was issued Friday afternoon.
MORE: Lloyd Austin takes 'responsibility' for keeping White House in the dark on hospitalizationThe surprise disclosure of Austin's hospitalization had raised questions inside and outside of government about why it was disclosed so late into his medical treatments.
Hicks had not been informed in advance and was on vacation in Puerto Rico when Austin was hospitalized, a U.S. official told ABC News. Hicks -- who has regularly made routine decisions on behalf of Austin -- was automatically tasked with assuming his authorities.
Austin is no longer in the ICU, but remained hospitalized Monday. He is making good progress and is in some discomfort, Ryder said.
"We do not have a specific date for his release from the hospital at this time but will continue to provide daily updates until then," Ryder said Monday evening.
ABC News' Sarah Beth Hensley contributed to this report.