The Pentagon has scaled back its plan to assemble an overseas spy service that could have rivaled the CIA in size, backing away from a project that faced opposition from lawmakers who questioned its purpose and cost, current and former U.S. officials said.

Under the revised blueprint, the Defense Intelligence Agency will train and deploy up to 500 undercover officers, roughly half the size of the espionage network envisioned two years ago when the formation of the Defense Clandestine Service was announced.

The previous plan called for moving as many as 1,000 undercover case officers overseas to work alongside the CIA and the U.S. military’s Joint Special Operations Command on counterterrorism missions and other targets of broad national security concern.

Instead, the training schedule has been cut back, and most of those involved will be given assignments that are more narrowly focused on the DIA’s traditional mission of gathering intelligence for the Defense Department.

The revised aim is to “stay small but be highly effective,” said a former senior U.S. intelligence official, who spoke on the condition of anonymity to discuss sensitive military planning.

The Pentagon will still be placing dozens of undercover officers “in very difficult places around the world,” including parts of Africa and the Middle East, where al-Qaeda and the Islamic State have significant footholds, the former official said. But their espionage efforts will “focus on what Defense needs are.”

Congressional resistance

The shift represents a retreat by Pentagon officials who had sought to transform a spy service long seen as second string to the CIA, repositioning it for an era of more dispersed threats after a decade of war in Iraq and Afghanistan.

The overhaul was spearheaded by Undersecretary of Defense for Intelligence Michael G. Vickers, a former CIA operative who has pushed to model the Pentagon’s spy service more closely on his former agency.

Aspects of that approach remain intact, including having members of the Defense Clandestine Service take part in the same instruction as their CIA counterparts at the agency’s training compound, known as the Farm, near Williamsburg.

Those who emerge from that training are expected to work in closer coordination with CIA station chiefs who have broad authority over U.S. espionage operations overseas.

But the initial scale of the plan has been reduced substantially, officials said, after it became clear that the proposal could not secure enough support and funding from Congress.

Defense Department officials declined to discuss details of the Defense Clandestine Service, including its budget or number of overseas positions, noting that such figures are classified. But the officials did not dispute that the plan for the DCS, as it is known at the Pentagon, has been scaled back.

“We did reevaluate the DCS program after initial discussions with Congress,” said Navy Cmdr. Amy E. Derrick-Frost, a spokeswoman for the Pentagon. Derrick-Frost emphasized that “it has always been a phased plan” that could take several years to implement and said that “there have been no significant changes” since a modified proposal was presented to Congress.

A senior U.S. intelligence official said the new numbers also reflect a different approach to the way officers in the Defense Clandestine Service are counted. He said initial projections included everyone who was considered part of the clandestine service, no matter where they were stationed. Now, he said, only those who are deployed overseas and gathering intelligence are part of the 500, meaning that those who are in assignments at headquarters or still undergoing training do not count toward that total.

“We don’t count people sitting at desks or people undergoing training,” the official said, meaning that the reduction in numbers is not as severe as it may sound because of the change in the way positions are counted. The official acknowledged that initial discussions for the DCS envisioned as many as 1,000 positions. “It was higher than where it is projected to be now,” he said.

Project’s cost questioned

The push to dramatically expand the DCS met almost immediate opposition on Capitol Hill, particularly from members of the Senate Armed Services Committee, many of whom were particularly hostile to the idea, in part out of concern that the terms were too generous to the CIA.

Sen. Carl Levin (D-Mich.), the chairman of the committee, and others raised concern that DIA officers would be used largely to fill in gaps in areas regarded as low priorities by the CIA, effectively doing aspects of that agency’s job at the Pentagon’s expense.

The Senate Intelligence Committee also found substantial problems with the DIA proposal. A report released by the panel last year said the plan “lacked details necessary for effective review and implementation.”

A senior Senate aide said Friday that the overhaul of the DCS “has been a continuing item of interest and careful review for the committee” even after the Pentagon’s revisions.

The struggle over the dimensions and direction for the Defense Clandestine Service has coincided with a turbulent time at the DIA, a sprawling espionage service that also has hundreds of analysts as well as defense attaches — embassy officials charged with gathering intelligence on foreign militaries — in more than 140 countries.

Former DIA director Michael Flynn — a retired major general who had held high-level positions in Afghanistan and Iraq — was pushed out of the DIA job earlier this year, well before his term was scheduled to end.

Many expected him to be replaced by Lt. Gen. Mary Legere, until her potential nomination encountered opposition on Capitol Hill. The job is now expected to go to Marine Maj. Gen. Vincent Stewart, who would be the first African American to lead one of the main U.S. intelligence agencies.

The agency is being led in the interim by David Shedd, a former senior CIA official.

The DIA’s operations have suffered in recent years outside the war zones. The former U.S. intelligence official cited cases in which the agency had as many as four case officers in some locations that had often failed to produce meaningful intelligence reports.

But the agency has also made strides in other areas. The former official said that the DIA now accounts for as much as 25 percent of the content that goes into the President’s Daily Brief, the prestigious summary of national security developments presented each morning to the president.

Unlike the CIA, the DIA is not authorized to carry out covert operations such as drone strikes or political sabotage. Its case officers, who carry out spy work overseas, often come from military backgrounds and serve under military cover abroad, meaning they hold positions in traditional military units even while covertly trying to steal secrets or persuade their foreign counterparts to become American informants.