Last year’s funding fight between Lockheed Martin’s Medium Extended Air Defense System (Meads) and Raytheon’s Patriot system has a sequel. Eight senators are asking their colleagues to shift funding from the U.S.-European missile defense system into upgrades for the current U.S. Army program.

“We are concerned that the Army has not yet presented to Congress a prioritized plan to support the long-term requirements for modernizing the Patriot system, which will be operational at least through 2042,” write the senators, all members of the Armed Services Committee, in a March 21 letter to the leaders of the Senate defense committees. “The President’s $400 million request for Meads would be better spent paying down our national debt or fully upgrading the Patriot system.”

The letter takes the argument a step beyond the scuffle that played out last year. Then, members of the armed services panel sought to kill funding for Meads because of problems with its development and management. Now they are asking for reinvestment of those dollars into the competing program.

In its fiscal 2012 budget request, the Pentagon said it needed $804 million over two years to complete development of Meads, made by a consortium led by Lockheed Martin, and fulfill its agreements with program partners Germany and Italy.

Senators including John McCain (Ariz.), the top Republican on the Senate Armed Services Committee, were frustrated by the program’s management difficulties. Pentagon statements that indicated it would not proceed with production of the system didn’t help. During the closed committee markup of the fiscal 2012 defense policy bill, McCain proposed killing funding for the system and was joined by a number of colleagues, but the amendment lost by one vote.

Still, the final fiscal 2012 defense authorization act fenced off 75% of the program’s $400 million for the year until the Pentagon submits a report on a plan to use the 2012 funds as “final obligations” for a reduced program or toward termination costs.

In the March 21 letter, Sens. Kelly Ayotte (R-N.H.), Mark Begich (D-Alaska), Jeanne Shaheen (D-N.H.), Scott Brown (R-Mass.), David Vitter (R-La.), Mark Udall (D-Colo.), Roger Wicker (R-Miss.) and Claire McCaskill (D-Mo.). stress that point in particular.

“The 2012 [defense authorization bill] clearly states that this year’s funds would be the ‘final obligations’ of funding for MEADS,” they write to McCain, Carl Levin (D-Mich.), Daniel Inouye (D-Hawaii) and Thad Cochran (R-Miss.). “We strongly urge you not to allow the Department of Defense to act in contravention of the law and to therefore not allocate any additional funding for Meads.”

McCain is sending a letter of his own to Defense Secretary Leon Panetta, challenging the Pentagon for continuing to request money for Meads. “I am disappointed that the Department has chosen to ignore current law and congressional direction by requesting an additional $400 million for Meads,” McCain writes. “I am similarly concerned by your remarks promising to do ‘everything possible’ to obtain congressional support for these additional funds.”

McCain, who has not yet received a report from the Pentagon about Meads, is asking Panetta to justify his funding request for the program.

Panetta made verbal commitments to the program’s funding during a visit last month by the German defense minister, after the German and Italian governments made clear the U.S. would face penalties for withdrawing from the effort.

The Pentagon used that argument to convince the Senate Appropriations Committee last year to provide full funding for Meads. And it appears that is the case again this year, according to a senior aide for Sen. Richard Shelby (R-Ala.), a member of the spending committee. If the U.S. withdrew from the program now, it would still have to pay an amount near the Meads budget request in termination costs, it would lose access to the system’s data rights and it would undercut allies on a key missile defense program, the aide says.