Concerns about costs and management has led Senate committee to oppose the Defense Department’s plans to increase number of spies overseas. (STAFF/AFP/GETTY IMAGES)

The Senate has moved to block a Pentagon plan to send hundreds of additional spies overseas, citing cost concerns and management failures that have hampered the Defense Department’s existing espionage efforts.

A military spending bill approved by the Senate last week contains language barring the Pentagon from using funds to expand its espionage ranks until it has provided more details on what the program will cost and how the extra spies would be used.

The measure offers a harsh critique of the Pentagon’s espionage record, saying that the Defense Department “needs to demonstrate that it can improve the management of clandestine [human intelligence] before undertaking any further expansion.”

The action is a setback for the Pentagon’s main spy service, the Defense Intelligence Agency, which has embarked on a five-year plan to assemble an espionage network overseas that is more closely modeled on the CIA and would rival that agency in size.

The plan is part of a broader effort to focus the DIA on broader threats — such as emerging al-Qaeda offshoots in Africa and Chinese military advances — after it spent the past decade concentrating on the wars in Iraq and Afghanistan.

The DIA has about 500 undercover operatives engaged in spying work overseas, but the plan calls for that total to climb to between 800 and 1,000 by 2018, officials said in an article published in The Washington Post on Dec. 2. The new operatives would be trained by the CIA and coordinate their assignments with CIA station chiefs overseas, but their main assignments would be determined by the Department of Defense.

Army Lt. Gen. Michael T. Flynn, director of DIA, has touted the plan in a series of recent speeches, saying it represents “a major adjustment for national security.”

Pentagon officials stressed that DIA has not been given additional authorities or permission to expand its total payroll. Instead, officials said, the extra spy slots would come by cutting or converting other positions.

The Senate measure, which was included in the fiscal 2013 National Defense Authorization Act, signals deep skepticism on Capitol Hill that the Pentagon can execute the plan.

The provision blocks the DIA from going beyond the number of human intelligence officers the agency had in place last April. It requires the Pentagon to produce “an independent estimate of the costs” of the new clandestine service, as well as a blueprint for where and when the newly hired spies would be deployed.

The language, drafted by the Senate Armed Services Committee, also instructs the Defense Department to turn over any agreements it has reached with other agencies — including the CIA — that would be involved in creating the Defense Clandestine Service.

The measure cites a litany of problems with existing Pentagon intelligence efforts, including “poor or non-existent career management” for operatives who have been trained but were given “unproductive” assignments overseas or were often transferred back to regular military units.

If the Pentagon could use existing resources more effectively, the measure concludes, ”the case could be made that investment in this area could decline, rather than remain steady or grow.”