WASHINGTON — The Pentagon will send hundreds of additional spies overseas as part of an ambitious plan to assemble an espionage network that rivals the CIA in size, US officials said.
The project is aimed at transforming the Defense Intelligence Agency, dominated for the past decade by the demands of two wars, into a spy service focused on emerging threats and more closely aligned with the CIA and elite military commando units.
The Defense Intelligence Agency is expected to have as many as 1,600 ''collectors'' around the world, an unprecedented total for an agency whose presence abroad numbered in the triple digits in recent years.
The total includes military attachés and others who do not work undercover. But US officials said the growth will be driven over a five-year period by the deployment of a new generation of clandestine operatives. They will be trained by the CIA and often work with the Joint Special Operations Command, but they will get their spying assignments from the Department of Defense.
Among the Pentagon's top intelligence priorities, officials said, are Islamist militant groups in Africa, weapons transfers by North Korea and Iran, and military modernization underway in China.
''This is not a marginal adjustment" for the Defense Intelligence Agency, its director, Lieutenant General Michael T. Flynn, said at a recent conference. He outlined the changes but did not describe them in detail. ''This is a major adjustment for national security.''
The sharp increase in undercover operatives is part of a far-reaching trend: a convergence of the military and intelligence agencies that has blurred their once-distinct missions, capabilities, and leadership ranks.
Through its drone program, the CIA now accounts for a majority of lethal US operations outside the Afghan war zone. At the same time, the Pentagon's plan to create what it calls the Defense Clandestine Service reflects the military's latest and largest foray into secret intelligence work.
The Defense Intelligence Agency overhaul — combined with growth of the CIA since the Sept. 11, 2001, terrorist attacks — will create a spy network of unprecedented size. The plan reflects the Obama administration's affinity for espionage and covert action over conventional force. It also fits in with the administration's efforts to codify its counterterrorism policies for a sustained conflict and assemble the pieces abroad necessary to carry it out.
Unlike the CIA, the Pentagon's spy agency is not authorized to conduct covert operations that go beyond intelligence gathering, such as drone strikes, political sabotage, or arming militants.
But the Defense Intelligence Agency has played a major role in assessing and identifying targets for US forces, which in recent years have assembled a constellation of drone bases from Afghanistan to East Africa.
The expansion of the agency's clandestine role is likely to heighten concern that it will be accompanied by an escalation in lethal strikes and other operations outside public view. The military is not subject to the same congressional notification requirements as the CIA.
US officials said the Defense Intelligence Agency's realignment would not hamper congressional scrutiny. ''We have to keep congressional staffs and members in the loop,'' Flynn said in October, adding that he believes the changes will help the United States anticipate threats.
US officials said the changes were enabled by a rare syncing of personalities and interests at the Pentagon and CIA.
''The stars have been aligning on this for a while,'' said a former senior military official involved in planning the Defense Intelligence Agency's transformation.
Former Defense Department officials said the agency now has about 500 ''case officers'' and the number is expected to reach 800 to 1,000 by 2018.