WASHINGTON – Two U.S. senators with sway over all federal spending have dealt a crippling bipartisan blow to the Pentagon’s troubled $2.7 billion program to use radar-carrying blimps to search for enemy missiles.

Sens. Thad Cochran, R-Miss., chairman of the Senate Appropriations Committee, and Richard J. Durbin, D-Ill., who holds the Democrats’ No. 2 leadership position in the Senate, have refused a request by the Obama administration to shift $27.2 million to the program to keep it alive.

Durbin now favors killing the blimp system, called JLENS.

“The JLENS program has been a big disappointment to taxpayers,” Durbin’s spokesman, Ben Marter, said in a statement. “It has cost nearly $3 billion . . It’s time to end the program.”

The request for the $27.2 million was sent to Congress last month by Defense Secretary Ashton Carter, who wanted the money to restart an operational exercise in which two JLENS blimps were supposed to stand sentry above the Washington, D.C., area.

Carter’s requested funding would have been on top of $45.5 million for JLENS included in President Barack Obama’s proposed budget for the coming fiscal year.

Because Carter had asked for money to be shifted, or “reprogrammed,” from another defense program, his request needed unanimous approval from eight of the most senior members of the Senate and House appropriations panels.

By Wednesday, Cochran and Durbin had quietly informed administration officials that they opposed the request. In addition to serving as Appropriations Committee chairman, Cochran leads the Senate Defense Appropriations Subcommittee, and Durbin is its ranking Democrat.

In a statement, Cochran’s spokesman, Chris Gallegos, indicated that JLENS was unlikely to receive support for any funding from the Senate.

The denial of the $27.2 million, Gallegos said, “is an indication that the administration’s ($45.5-million) budget request for JLENS is likely to receive an icy reception from the committee.”

The comments suggested that the dramatic breakaway last fall of a JLENS blimp from its mooring at the Army’s Aberdeen Proving Ground in Maryland was a final straw for congressional appropriators. The blimp was one of two participating in the operational exercise to protect the capital region.

For several hours on Oct. 28, the pilotless, 242-foot-long blimp sailed over Maryland and into Pennsylvania, disrupting commercial air traffic and clipping utility lines with its mile-long tether. About 35,000 rural Pennsylvania residents had lost power by the time the blimp came to rest in the woods of northern Pennsylvania, 150 miles from its base.

An Army investigation found that JLENS support personnel had failed to load batteries to power an automatic deflation device that should have brought the blimp to the ground within two miles.

Durbin’s spokesman said that the operational exercise was an opportunity for JLENS to prove its usefulness, and that “it failed spectacularly.” He also pointed to Pentagon reports documenting poor performance by JLENS on test ranges.

Durbin’s opposition to the funding was first reported Friday by Politico.

JLENS is short for Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System. It is designed to provide surveillance of low-altitude threats such as cruise missiles and drones.

In tests, the JLENS radar has struggled to track flying objects and to distinguish friendly aircraft from potential threats.

A Los Angeles Times report published in September described how backers of JLENS at the Pentagon and at Raytheon maneuvered to keep taxpayer money flowing to the problem-plagued program.

In late 2010, the second-ranking Army leader – Gen. Peter W. Chiarelli – tried to kill JLENS. Chiarelli was trumped by the then-vice chairman of the Joint Chiefs of Staff, Marine Gen. James E. “Hoss” Cartwright, who backed plans for what became the operational exercise, a lifeline for the program.

Cartwright retired from the military in late 2011 – and five months later went on Raytheon’s payroll as a director. In his first three years on its board, Raytheon paid Cartwright more than $828,000 in cash and stock, records show.

Other doubts about JLENS emerged Friday from two Maryland lawmakers who had staunchly backed the program.

Sen. Barbara A. Mikulski, D-Md., issued a statement expressing “very grave reservations about both the program’s safety for local communities and its national security accomplishments.”

Rep. C.A. Dutch Ruppersberger, D-Md., said he too now opposed spending the additional $27.2 million to restart the exercise.

The breakaway of the blimp “jeopardized the safety of my constituents,’” said Ruppersberger, who serves on the House Appropriations Committee. “I can’t, in good conscience, support its continuation in such a highly populated area.”