WASHINGTON  President Obama has picked Lt. Gen. James R. Clapper Jr. as director of national intelligence, tapping a retired officer with decades of experience to improve coordination of the nation’s sprawling spy apparatus amid increasing threats at home and escalating operations abroad.

Mr. Obama plans to announce his choice in the Rose Garden on Saturday, two weeks after forcing Adm. Dennis C. Blair out of the spymaster job, according to administration officials, who insisted on anonymity to disclose the decision before the formal ceremony.

The selection amounts to pushing the reset button for the president as he tries to recalibrate an intelligence structure that has undergone continued revamping since the debacle leading up to the Iraq war, yet by most accounts still lacks the cohesion necessary in an evolving war with terrorists. Even as intelligence agencies expand their role overseas with drone strikes in Pakistan and increased focus on Yemen and Somalia, they have faced a spate of attempted attacks in the United States.

General Clapper, 69, who retired in 1995 after 32 years in the Air Force, rose from a signals intelligence officer to undersecretary of defense for intelligence, overseeing all military spy operations. In picking him, the president found an intelligence veteran who clashed with Defense Secretary Donald H. Rumsfeld and was pushed out of office as a result, only to return to the Pentagon as a top lieutenant to Defense Secretary Robert M. Gates.