Good news: President Obama has discovered an area of the federal budget where he wants to spend less money. Bad news: It's defense.

According to Bob Woodward's new book, "Obama's Wars," when someone raised the subject of a long-term American military presence in Afghanistan President Obama replied with "I am not spending a trillion dollars." Spending on defense overall, in fact, has slowed considerably, especially when compared to other areas of the budget.

Worse, the president has championed deep cuts in missile defense and signed a New START agreement with Russia that limits our future missile-defense capabilities. This comes amid a looming threat from abroad. According to a new report from the Institute for Science and International Security, North Korea has "moved beyond laboratory-scale work" and has the "capability to build" a highly enriched uranium-producing centrifuge plant.

Now, budget-cut proposals usually deserve applause. They're seldom seen in Washington, where spending is an all-consuming hobby for all too many policymakers. But this interest in fiscal austerity is, unfortunately, rather suspect. It would be more reassuring if it weren't for a couple of important facts.

For one, President Obama is fully behind a federal budget that would keep the money spigot turned wide open. According to the Congressional Budget Office, his proposed budget for 2011 will add $10 trillion in debt over the next decade. By 2020, the federal government will owe $20 trillion, or $170,000 per American household. Polls show that many Americans routinely overestimate the amount the federal government spends on defense. It's much smaller than people realize. Even with the costs of Iraq and Afghanistan, this year the Department of Defense will spend some $720 billion. That sounds like a lot, but it's only about 4.9 percent of our gross domestic product. It's well below the average of 6.5 percent since World War II.

Here's the second fact that helps put the issue in context: National security is one of the first and most important responsibilities of the federal government. It's right there in Article 1, Section 8 of the Constitution: "The Congress shall have the power to ... provide for the common defense."

Of course, that doesn't mean policymakers should spend wantonly on any defense program that comes along. But it does suggest that when the government is running full-tilt into deficit territory - and it certainly is now - we should check other areas of the budget for savings before cutting into the part devoted to keeping us all alive.

As I noted in an Op-Ed I wrote with Arthur Brooks and William Kristol for the Wall Street Journal, defense spending has increased at a much lower rate than domestic spending in recent years. Even while fighting two wars, the core defense budget has risen about $220 billion since 2001, about a 10th of what the government devotes each year to "mandatory" spending: Social Security, Medicare, Medicaid, entitlements such as food stamps and cash assistance and interest payments on the debt. These expenditures continue automatically, year after year, without congressional debate.

We should consider no corner of the budget off-limits in our search to eliminate waste. But anyone seeking to restore our fiscal health should look first at entitlements, not at across-the-board cuts aimed at our men and women in uniform.

The United States can attribute its standing in the world to many things, but having the strongest, most capable military is a huge factor behind our success. Spending what's necessary to ensure that we stay the best is one of the most basic jobs our elected leaders have. We simply cannot afford to shortchange our security.

Ed Feulner is president of the Heritage Foundation.