Twenty-three years ago last week, citizens stood atop the Berlin Wall and began tearing it down — erasing one of the most pronounced scars of the Cold War. Yet, decades later, the United States is still coping with one of its biggest Cold War legacies — a bloated nuclear arsenal.

In a time when tough budget choices need to be made to avoid the looming fiscal cliff, there is a major question before Congress — will America spend $640 billion on nuclear weapons and related programs or reshape our military budget to match 21st-century realities? Two decades after the wall fell, it’s a question that demands immediate attention.

A lot has changed since 1989. Europe is now whole, and the Soviet Union is no more. Nuclear terrorism, not mutual annihilation, has become the United States’ primary concern. Where Washington once worried about nuclear launch orders from Moscow, today Apple is more worried about iPad launch orders in Moscow.

Yet the United States still maintains a Cold War nuclear posture with thousands of nuclear weapons in its stockpile.

As former STRATCOM Chief Gen. James Cartwright recently testified that “the current U.S. nuclear force remains sized and organized operationally for fighting the ‘last war’ — the Cold War — even though threats from that era posed by the Soviet Union and China have greatly diminished or disappeared.” Cartwright noted, “Ample latitude exists for further nuclear cuts.”

Cartwright is one among many defense experts who agree that the United States would be better off strategically with fewer nuclear weapons.

The nuclear arsenal is also extremely expensive.

The United States is on track to spend about $640 billion on nuclear weapons and related programs over the next 10 years.

A huge portion of those funds are slated for replacing nearly every part of the arsenal, which would entrench a Cold War nuclear strategy well into the end of this century.

Included in the overhaul are funds for a $10.4 billion nuclear bomb program that would allow U.S. tactical nuclear weapons to remain in Europe. When the Soviet Union dissolved, President George Bush quickly pulled such weapons out of Europe by the thousands. After 20 years without an adversary to deter, the few remaining weapons are costing billions to keep.

More funds are slated for a $55 billion program to buy a new bomber, a series of programs to keep ICBMs (still directed at Russia) in service for decades, and several multibillion-dollar projects to increase the capacity of the nuclear weapons production complex. All of this is planned even as the size of the arsenal is decreasing.

These programs have diminishing relevancy for U.S. national security, but they are increasingly siphoning funds from other more pressing priorities. Remarking on the size of America’s nuclear arsenal, former Secretary of State Colin L. Powell said, “We have every incentive to reduce their number. These are expensive. They take away from soldier pay.” He added, “They take away from lots of things. There is no incentive to keep more than you believe you need for the security of the nation.”

The threats America faces today are a lot different than those of the 1980s. It’s time our outdated nuclear policies changed too.

A smarter nuclear strategy would reduce our arsenal and forgo the costly investments needed to overhaul it. It can be done. Walter Pincus of The Washington Post estimated that focused nuclear cuts could save $100 billion over the next 10 years. That is a solid start.

Decades after the Berlin Wall came down, its makes no sense for the nuclear weapons budget to get built up. The major challenges of modern times — from terrorism to cyber-war — demand a new strategy and focused resources to confront them.

It’s clear we have a nuclear spending problem — the $640 billion dollar question is, will Congress fix it?

Benjamin Loehrke is a senior policy analyst at Ploughshares Fund.