Further reductions in nuclear weapons beyond those agreed to in the New START agreement with Russia are being discussed within the Obama administration as part of the Defense Department review of future spending.

Maybe it is time for thinking outside what is still a Cold War nuclear box, which focuses on the United States having enough secure nuclear weapons to deter some other country from using theirs against America or its allies, today or in the future.

The Pentagon discussions are mainly about whether savings can be made in the $213 billion or more that the Defense and Energy departments require over the next 10 years to modernize the current triad of strategic intercontinental-ballistic-missile-launching submarines, land-based ICBMs and long-range bombers, and to upgrade the aging industrial complex that builds and maintains the nuclear warheads and bombs in the stockpile.

Defense Secretary Leon E. Panetta has “indicated that there’s been preliminary discussion about maintaining an effective nuclear deterrence capability while reducing the size of our nuclear arsenal.” That’s the way Defense Department spokesman George Little has put it.

The Pentagon review is looking at “strategic needs,” which means threats that could or should be deterred by the U.S. nuclear forces. Based on that, it will study the existing U.S. nuclear “force structure,” which means numbers and types of delivery systems and warheads. And, finally, it will look at U.S. “force posture,” or how many U.S. warheads need to be deployed on sub- or land-based ICBMs or bombers, and whether they should be on alert or in reserve stockpiles.

Cost estimates for replacing these three delivery systems have already grown 25 percent over the past year. During the 2010 debate over the treaty with Russia, the estimate for replacing the strategic submarines, land-based ICBMs and strategic bombers together was $100 billion over 10 years. It is now $124.8 billion, as James N. Miller, principal deputy undersecretary of defense for policy, told the House Armed Services strategic forces subcommittee on Nov. 3.

What are we talking about for the long run? The ranking Democrat on the subcommittee, Rep. Loretta Sanchez (Calif.), said the current nuclear forces modernization plan estimated that the cost of building just the new fleet of strategic submarines would be $110 billion, but out more than 10 years. The estimate for operating them would be another $250 billion over their 50-year life span.

The Air Force estimate for 100 new strategic bombers, manned or unmanned, is an additional $55 billion, and there is no figure yet for a new generation of land-based ICBMs, she said.

In his April 2009 Prague speech, President Obama said, “To put an end to Cold War thinking, we will reduce the role of nuclear weapons in our national security strategy and urge others to do the same.” Today’s goal, required by New START, is to have 1,550 deployed warheads on 700 delivery systems by 2018.

Those numbers represent Cold War thinking. They relate to Russia’s forces and what’s needed to deter Moscow. But deter Moscow from what? For that matter, how does the U.S. stockpile of 1,550 warheads deter China, or al-Qaeda or other non-state terrorist groups? U.S. nuclear warheads have not deterred North Korea from trying to build their own, nor do they deter Iran. They may have encouraged their programs.

That number does deter one group — Obama’s political opponents. Let’s face it, nuclear weapons for decades have primarily been political weapons, both domestically and abroad. If you have more than your enemies, you are a strong leader. Faced with an international crisis, that leader can say “nothing is off the table” — and that can be read as a threat to employ nuclear weapons.

But despite what defense planners say about actually using them only against valued military targets, they are in fact weapons that will kill thousands of civilians either immediately or through radioactive aftereffects. Two atomic bombs, far less powerful than today’s warheads, used twice against Japanese “military targets” destroyed two cities and killed or wounded hundreds of thousands of civilians.

Would a U.S. president use one or more nuclear weapons first, or only if the United States were attacked? In either event, this country does not need 1,000 or more of them. Nor do we need all of the 12 new $4 billion strategic nuclear submarines, each with 16 missiles. Each missile carries a minimum of four warheads. With only nine such subs, the United States could have three on patrol, two in the Pacific and one in the Atlantic, and the United States would have a minimum of 192 warheads ready to hit targets all over the world.

With such an underwater fleet, do we still need up to 400 new land-based ICBMs? And why have any strategic bombers fitted to carry nuclear weapons?

Years ago, Robert McNamara — defense secretary through much of the 1960s — told me he had always believed that 500 warheads or less was enough, even at the height of the Cold War. He based that on recalling one night during the October 1962 Cuban missile crisis when, during a private meeting with President John F. Kennedy, they discussed the impact just one nuclear weapon would have on the United States if fired by Moscow, and what the president would have to order in response.

“As I walked out of the White House and to my car,” McNamara said, “I feared we might end the world as it was unless we prevented that from happening.” They did, and from then on, both Washington and Moscow over the years avoided another such direct or indirect confrontation.

Nuclear weapons deterred conventional war between the world’s then-superpowers. But neither country ever needed the more than 10,000 each had built. According to McNamara, several hundred would have been enough then, and it certainly would be enough now. The United States today can’t afford the Cold War luxury of overbuilding its nuclear force, and that could be a blessing.