WASHINGTON — A bipartisan group of U.S. senators is calling for the cancellation of a multinational air and missile defense system, citing cost overruns and a tight budget environment.

Eight senators — including four Democrats and four Republicans — signed a March 21 letter calling on the leaders of the Senate Appropriations Committee and Senate Armed Services Committee to reject the Defense Department’s request for $400 million in 2013 to continue work on NATO’s Medium Extended Air Defense System (MEADS).

“Facing a serious fiscal crisis, we cannot afford to spend a single additional dollar on a weapons system such as MEADS that our warfighters will never use,” the senators wrote.

Sen. John McCain, (R-Ariz.), the ranking member of the Senate Armed Services Committee, followed up with a March 22 letter of his own to Defense Secretary Leon Panetta reminding him that the 2012 National Defense Authorization Act directed the Pentagon to negotiate with Germany and Italy to either terminate MEADS or restructure the program so that it can be completed within the $390 million Congress appropriated for this year.

“I am disappointed that the Department has chosen to ignore current law and congressional direction by requesting an additional $400 million for MEADS in fiscal year 2013 to continue the ‘proof of concept’ that Congress instructed be completed utilizing no more funding than the level appropriated for fiscal year 2012,” McCain wrote. “I am similarly concerned by your recent remarks promising to do ‘everything possible’ to obtain congressional support for these additional funds.”

Citizens Against Government Waste, a nonpartisan watchdog group here, released a report March 26 calling for the cancellation of MEADS. “Although diplomatic and contractual concerns need to be taken into consideration, the best course of action would be for the allies to collectively cancel the program,” said Tom Schatz, the group’s president.

Lockheed Martin, the lead U.S. contractor for MEADS, has not given up hope on seeing the embattled program through to production. Marty Coyne, the company’s director of MEADS International, told Space News April 3, Lockheed Martin is “cautiously optimistic” that the program will receive full funding in 2013.

MEADS is intended to replace the U.S. Army’s aging Patriot air and missile defense system and has been in development for more than a decade. MEADS is designed to use mobile trucks equipped with interceptor missiles and omni-directional radars to defeat cruise missiles and short-range ballistic missiles in the terminal phase of flight. The system is funded 58 percent by the United States, 25 percent by Germany and 17 percent by Italy.

The group of eight U.S. senators urging the immediate cancellation of MEADS includes Sens. Scott Brown (R-Mass) — whose state is home to Patriot prime contractor Raytheon Co. — and Jeanne Shaheen (D-N.H.) and Kelly Ayotte (R-N.H.), whose New England state is home to at least one Raytheon subcontractor.

“While the Pentagon has continued to waste tax dollars on MEADS, the Department of Defense has failed to fully modernize its Patriot program,” the senators wrote.

In addition to Brown and New Hampshire’s two senators, the letter’s other signatories are: Mark Begich, (D-Alaska),  Mark Udall (D-Colo.), Claire McCaskill, (D-Mo.), David Vitter (R-La.) and Roger Wicker (R-Miss.).

The 2012 National Defense Authorization Act called for fencing off all but 25 percent of the approved $390 million in 2012 funding until the defense secretary submits a plan for using those funds for “final obligations” for the MEADS program. That plan can outline scenarios for restructuring the program or terminating the program contracts, according to budget documents. Coyne said that he expects that plan to be delivered to Congress in a matter of days.

Coyne also said that the United States contacted Germany and Italy but those two countries do not want to restructure the program. Lockheed Martin officials plan to conduct additional testing of MEADS in 2012, he said. The MEADS program has been on-schedule and within projected costs since 2008, Coyne said.