Defense Secretary Lloyd J. Austin III will not travel to Brussels to meet with his NATO and European counterparts this week, a Pentagon official said on Monday, as he remained hospitalized for complications stemming from prostate cancer surgery.

Mr. Austin, 70, returned to the hospital on Sunday, for the third time in two months, with “symptoms suggesting an emergent bladder issue.” He had initially intended to “retain the functions and duties of his office” but soon turned over his authorities to the deputy defense secretary, Kathleen Hicks.

It was unclear how long Mr. Austin was expected to remain at Walter Reed National Military Medical Center in Bethesda, Md., where he was taken on Sunday. In a statement, Dr. Gregory Chesnut and Dr. John Maddox said that Mr. Austin underwent nonsurgical procedures on Monday “under general anesthesia to address his bladder issue.”

“A prolonged hospital stay is not anticipated,” the doctors said, adding that they expected that Mr. Austin would “be able to resume his normal duties tomorrow.”

Brig. Gen. Patrick S. Ryder, the Pentagon spokesman, told reporters that Celeste Wallander, the assistant secretary of defense for international security affairs, would represent the United States at a meeting on Ukraine in Brussels on Wednesday. He also said that the American ambassador to NATO, Julianne Smith, would represent Mr. Austin at a NATO defense ministers meeting in Brussels on Thursday.

Mr. Austin, General Ryder said, may attend the Wednesday meeting virtually if his health allows. Gen. Charles Q. Brown Jr., the chairman of the Joint Chiefs of Staff, is also expected to attend Wednesday’s meeting virtually, General Ryder said.