Defense Secretary Leon Panetta warned yesterday that if the Pentagon receives the largest-possible budget cuts, weapon programs including the F-35 Joint Strike Fighter, the next-generation bomber, the Littoral Combat Ship, ground-combat vehicles, and European missile defense could be cancelled.

Panetta detailed the impacts of the so-called sequestration process–which would deal the Pentagon up to $600 billion in additional cuts if a congressional committee fails to craft a federal-budget-cutting plan–in a letter yesterday to Sens. John McCain (R-Ariz.) and Lindsey Graham (R-S.C.). The Budget Control Act of 2011 already reduces planned Pentagon spending by $450 billion over the next decade, but if the Joint Select Committee on Deficit reduction does not craft a plan to cut $1.2 trillion in addition federal spending by Nov. 23, which then passes Congress by Dec. 23, the sequestration process would be triggered and bring the tally to roughly $1 trillion over a decade. Those cuts would be in comparison to the Pentagon’s spending plans proposed in advance of fiscal year 2012.

“The impacts of these cuts would be devastating for the (Defense) Department,” Panetta wrote yesterday to McCain and Graham, in response to their request for information.

The two senior Senate Armed Services Committee (SASC) members have been working on a plan to prevent or lessen the automatic defense cuts under the potential sequestration process.

“We are staunchly opposed to this draconian action,” McCain and Graham said yesterday in a statement about sequestration. “This is not an outcome that we can live with, and it is certainly not one that we should impose on ourselves. The sequester is a threat to the national security interests of the United States, and it should not be allowed to occur.”

Panetta wrote to them that he believes “it is essential that the Joint Select Committee on Deficit Reduction (JSCDR) meet its target and avoid sequestration” and strongly urges the panel to “meet its target while following the president’s proposals, including his recommendation not to impose further reductions in the caps on discretionary funding.”

If sequestration is triggered, he said, the FY ’13 reduction in defense spending would total 23 percent, provided the president exercised his authority to exempt military personnel from the reductions. That 23 percent cut would have to be applied equally to each major investment and construction program, under current law.

“Such a large cut, applied in this indiscriminate manner, would render most of our ship and construction projects unexecutable–you cannot buy three quarters of a ship or a building and seriously damage other modernization efforts,” Panetta said.

Going forward, cutting the Pentagon budget by $100 billion a year compared to FY ’12 plans–which would happen under the worst-case cuts–would lead to “the smallest ground force since 1940, the smallest number of ships since 1915, and the smallest Air Force in its history,” he wrote.

We would also be forced to terminate most large procurement programs in order to accommodate modernization reductions that are likely to be required,” he said.

Panetta also sent the senators a document listing “potential effects” of sequestration. It warns the worst-case cuts, which could lead to a reduction of nearly 20 percent in defense funding over the next decade, could force the Pentagon to:

– terminate the F-35 and make “minimal life extensions and upgrades to existing forces” (for $80 billion in savings);

– cancel the Air Force bomber effort and restart a new program in the mid-2020s ($18 billion);

– delay the next-generation ballistic-missile submarine and cut the force to 10 subs ($7 billion);

– terminate the Littoral Combat Ship and its mission modules ($22 billion);

– end all ground combat vehicle modernization programs and make minimal life extensions and upgrades to existing forces ($17 billion);

– terminate all Army helicopter modernization programs and make minimal life extensions and upgrades to existing forces ($11 billion);

– delay or kill major space initiatives including space protection, communications satellites, and intelligence, surveillance, and reconnaissance (ISR) systems ($27 billion);

– terminate European missile defense ($2 billion);

– delay or cancel unmanned ISR systems ($8 billion); and

– eliminate the intercontinental ballistic missile leg of the nuclear triad ($8 billion).