As the Obama administration and Congress move forward with a multifaceted economic-stimulus package with a price tag of hundreds of billions of dollars, yet another interest group has staked its claim to a share of those funds -- the nation's defense contractors.

The arms lobby and its supporters in the think-tank world have made their case in a series of ads, articles and talking points. Martin Feldstein of the American Enterprise Institute describes defense spending as a "great stimulus." Weekly Standard editor Bill Kristol agrees. Noting that the military was "spending all kinds of money already," Mr. Kristol wondered aloud, "If you're buying 2,000 Humvees a month, why not buy 3,000? If you're refurbishing two military bases, why not refurbish five?"

Such comments ignore that military spending is supposed to serve one central purpose: advancing U.S. security. The defense budget is not a jobs program, nor should it be. Decisions on how many Humvees to buy, or how many bases to refurbish, should rest on military necessity, not economic expedience subject to political chicanery. When military procurement becomes nothing more than a series of thinly veiled pork-barrel projects, it risks exposing our troops to unnecessary risks, and ultimately undermines our security.

This is not the first time that defense spending has been endorsed as a way to jump-start the economy. Nearly five decades ago, economic advisers to President Kennedy urged him to increase military spending as an economic stimulus. In a report for the incoming administration, Paul Samuelson warned that such spending ought not be "the football of economic stabilization," but maintained that "any stepping-up of [defense] programs that is deemed desirable for its own sake can only help rather than hinder" the health of the economy.

Similar arguments are heard today. The members of Connecticut's congressional delegation have been particularly outspoken in their support for the Virginia-class submarine, and they haven't been shy about pointing to the jobs that the program provides in their home state. The Marine Corps' V-22 Osprey program wins support on similar grounds. Despite serious concerns about crew safety and comfort, the V-22 program employs workers in Pennsylvania, New Jersey, Delaware and Texas, and a number of other states.

Or take the case of the F-22 combat aircraft. The Pentagon had pledged to cap the F-22 program at 183 aircraft - a sensible decision, given that our most dangerous adversaries are al Qaeda terrorists and Taliban insurgents that don't possess even a single aircraft. The Air Force tried to send F-22s to Iraq, but Defense Secretary Robert M. Gates denied their request.

Undaunted, the arms industry, the Air Force and their friends in Congress are attempting to keep the production line open indefinitely. At more than $350 million each, the F-22 is the most expensive fighter plane ever built. Buying more now will distort the defense budget and crowd out other projects that are more relevant to the threats we face.

Plans to add tens of thousands of personnel to our armed forces will have a similar distorting effect. The resulting payroll increases will come at a high price to taxpayers and to our long-term security. As the war in Iraq winds down, there is no obvious reason to increase the size of our military, especially since we shouldn't be planning to fight more Iraq-style wars. It makes far more sense to ensure that we maintain or improve the quality of the existing force than it does to add numbers for numbers sake.

Consideration of the potentially beneficial economic effects of Pentagon spending merely impedes our ability to build and maintain the military we need. Politicians should not be rewarded for pushing projects that do not align with our strategic objectives.

Using the Pentagon budget as a source of economic stimulus is a bad bargain. President Obama should resist calls for more military spending while his administration reorients the Pentagon's budget to reflect a new, more realistic set of security goals.