Defense Secretary Lloyd J. Austin III appeared at the lectern of the Pentagon briefing room on Thursday to take questions from reporters for the first time in more than a year, beginning what is expected to be a protracted period of explaining why he kept the public, and the president, in the dark for weeks about his prostate cancer and surgery.
“We did not handle this right; I did not handle this right,” Mr. Austin said. “I should have told the president about my cancer diagnosis. I should have also told my team and the American public, and I take full responsibility.”
Mr. Austin also said that he never told his staff not to inform the White House about his hospitalization.
The defense secretary, long known as an extreme introvert who loathes talking about himself in public, sought to explain why he kept quiet about an illness that he described as a “gut punch.”
Mr. Austin said his first instinct was not to say anything. He said doctors told him that he had a narrow window to get his surgery, and he decided to have it just before Christmas, thinking that was a time when he was expected to be away from work. Mr. Austin said that he thought President Biden had enough to worry about without having to be concerned about the personal problems of his defense secretary.
“When you’re president of the United States, you’ve got a lot of things on your plate,” he said. “I just didn’t feel that that was a thing that I should do at the time. But again, I recognize that that was a mistake.”
Mr. Austin was transported to the news conference room in a golf cart 45 minutes before the scheduled start of the conference and walked slowly, using a cane, to a green room to prepare with his aides. He did not have a cane when he walked to the lectern.
The defense secretary was widely criticized for failing to immediately disclose his illness and absence to the White House, a breach of protocol that baffled officials across the government, including at the Pentagon.
The House Armed Services Committee has asked Mr. Austin to testify this month about why he and his aides kept his illness secret. The committee’s chairman, Representative Mike D. Rogers, Republican of Alabama, said that “Congress must understand what happened and who made decisions to prevent the disclosure of the whereabouts of a cabinet secretary.”
Mr. Austin, 70, has long been known as an intensely private man who eschews the limelight and dislikes talking to the news media — qualities that Mr. Biden was fine with, his aides said, when he appointed the 40-year Army officer to be his defense secretary.
But in keeping his hospitalization secret, Mr. Austin attracted more attention to himself than at any point in his long career. He also drew criticism of Mr. Biden’s national security team during a period of multiple crises around the world, including wars in Gaza and Ukraine.