A Republican senator on a leading defense panel in Congress has moved to block the Air Force's plans to retire the A-10 Warthog attack plane.

Sen. Kelly Ayotte, R-N.H., working with Sen. Roy Blunt, R-Mo., has introduced an amendment to the 2014 National Defense Authorization Act that would limit the service's ability to retire the aircraft. The legislation sets policy goals and spending targets for the fiscal year that began Oct. 1.

Ayotte recently led a group of more than 30 lawmakers in writing a letter to Defense Secretary Chuck Hagel and Chairman of the Joint Chiefs of Staff Army Gen. Martin Dempsey arguing against the Air Force's plan to divest the decades-old aircraft beginning in fiscal 2015. Service officials floated the idea as a way to save money amid automatic budget cuts known as sequestration.

"The A-10 plays an essential role in helping our ground forces and special operators accomplish their missions and return home safely," the Nov. 15 letter states. "We oppose any effort that would divest the A-10, creating a CAS capability gap that would reduce Air Force combat power and unnecessarily endanger our service members in future conflicts."

Known officially as the Thunderbolt II and more commonly as the Warthog, the plane entered military service in the late 1970s and flew in Iraq, Afghanistan and Libya.

The Air Force maintains A-10 squadrons in multiple states in the U.S., and at bases in Germany and Korea. The service has more than 340 of the aircraft across the active, National Guard and Reserve components, according to a fact sheet.

The twin-engine aircraft is designed to decimate tanks, vehicles and other ground targets with its GAU-8 Avenger, a 30mm seven-barrel Gatling gun, and up to 16,000 pounds of ordnance, including Mk-82 Mk-84 bombs, AGM-65 Maverick missiles and laser-guided munitions, according to the fact sheet.

The Air Force spent more than $1 billion in recent years upgrading the A-10 fleet. Boeing Co. received contracts worth hundreds of millions of dollars to replace the aircraft's wings. The service on Tuesday awarded a $24 million order to Northrop Grumman Corp. to modernize the aircraft's weapons system to keep it viable through 2028.

To find long-term budget savings, however, the service is considering shedding its fleets of "single-mission" aircraft -- not only the A-10, but also the KC-10 refueling tankers and F-15C fighter jets, officials said at the Air Force Association's Air & Space Conference and Technology Exhibition in September at National Harbor, Md.

"Everything is on the table," Acting Air Force Secretary Eric Fanning said at the time. "We are looking most closely at single-mission fleets."

The Defense Department faces $500 billion in automatic cuts through fiscal 2021. That's in addition to almost $500 billion in defense reductions already included in 2011 deficit-reduction legislation.

The first installment of the across-the-board cuts totaled $37 billion and began March 1 after lawmakers were unable to reach an alternative agreement on taxes and spending. The next round totals $52 billion and is set to take effect Jan. 1.

The amendment introduced by Ayotte would prevent the service from retiring the A-10 until Fanning or his successor certifies to Congress that its planned replacement, the F-35 Lightning II fighter jet, is fully ready to fly combat operations -- which is still years away.

Air Force Chief of Staff Gen. Mark Welsh recently testified that the F-35A, the service's version of the stealth fighter designed for conventional take-offs and landings, won't reach so-called full operational capability until 2021.

The F-35 Joint Strike Fighter is the Defense Department's most expensive weapons program, estimated to cost $391 billion to develop and build 2,457 aircraft, according to budget documents. The fifth-generation, single-engine jet is designed to replace the A-10, F-16, F/A-18 and AV-8B aircraft.

Ayotte's amendment would also require that the F-35 run a version of software known as Block 4A, which includes enhanced electronic warfare functions for close-air support and the ability drop a GBU-53 Small Diameter Bomb version II or its equivalent, according to a copy of the text.

Software development has been problematic for the program. The Air Force, for example, plans to begin flying missions with the F-35 in 2016 using a less lethal version of the software known as Block 2B. Lockheed Martin Corp., the world's largest defense contractor and the main manufacturer of the F-35, in June said it reassigned some 200 engineers to work on the computer code.

The amendment would also require Comptroller General Gene Dodaro, the head of the Government Accountability Office, the investigative arm of Congress, to submit a report to lawmakers on the Air Force's plans for the A-10.

The Senate began debating the defense legislation on Tuesday and is expected to vote on the bill before leaving Thursday for an 11-day Thanksgiving recess. The House, meanwhile, has already passed its version of the legislation.