The risks of debilitating cuts to our national-security budget will be a critical issue for Congress when it reconvenes after the August recess. While the media focus as Congress adjourned earlier this month was on the big-picture implications of the legislation lifting the federal debt-ceiling, we cannot lose sight of the difficult -- and imminent -- struggles just ahead in September.

Critical appropriations measures for Fiscal Year 2012 (“FY 2012,” beginning October 1) will have a major impact not just in the immediate future, but will also set the stage -- and budget baselines -- for future force levels, research and development, weapons procurement, and budget allocations.

Resources for the continuing conflicts in Iraq and Afghanistan are, of course, also critically important, and should reflect what is necessary to support our troops fully. But we must also necessarily keep our ongoing defense needs in the center of any broader budget decisions. Dollars well spent for our national security are simply not fungible with expenditures elsewhere in the federal budget.

The central point of concern in September will be the Senate Appropriations Committee. Many analysts believe that the Committee’s budget allocation for FY 2012 defense spending will be approximately $525 billion, or roughly $ 4 to 5 billion below the level appropriated for FY 2011, the current fiscal year. (Other estimates place the figure as low as $ 520 billion.) A basic defense spending level of $ 525 billion for FY 2012 amounts to a reduction of approximately $ 28 billion from even President Obama’s request level of $ 553 billion.

The House appropriations level for FY 2012 is $530 billion, essentially the same as the current fiscal year, despite the House’s own endorsement of the President’s level when it adopted Rep. Paul Ryan’s budget resolution.

Thus, whether Congress accepts the House number for FY 2012 ($23 billion below the Obama level) or an even lower Senate number, there will be substantial defense cuts below even the parsimonious Obama request. Also at risk under both the House and Senate numbers are funds required for nuclear weapons and infrastructure modernization, provided in another appropriations bill.

These near-term cuts for defense are disproportionate and unsustainable. They will cause palpable damage to our defense capabilities now and well into the future.

In March, 2011, then-Secretary of Defense Gates said that “it is my judgment that the Department of Defense needs an appropriation of at least $ 540 billion for FY 2011 for the U.S. military to properly carry out its mission, maintain readiness, and prepare for the future.” (emphasis added)

But neither the House nor projected Senate levels for FY 2012 are at $ 540 billion, nor do they include even a minimal increase in Secretary Gates’ benchmark level to adjust for inflation over the prior fiscal year.

This looming debacle must be a priority for House and Senate Republicans when they return from the recess. While national-security authorizers and appropriators will be responsible for the budget specifics, they cannot guarantee adequate top-line defense spending without the fullest support and protection from both their leaderships and the full party caucuses in both the House and Senate. Pro-defense Democrats must also step forward, especially in the Senate where their party holds the majority, and effective control of floor debate.

The upcoming crucial battles over appropriations levels for FY 2012 will almost certainly foreshadow the negotiations in the congressional Joint Select Committee on Deficit Reduction established by the federal debt-ceiling legislation.

If we fail to protect America’s defenses in the FY 2012, budget, we can only expect to fail in the Joint Committee’s deliberations, and thereby fall prey to the budget guillotine inherent in the debt-ceiling legislation’s “trigger mechanism.” That trigger could produce even further defense cuts in the range of $ 500 to 600 billion.

Hollowing out America’s military would be a catastrophic mistake in a dangerous world. Recent press reports alone have highlighted, among other threats and challenges:

(1) The continuing dangers in Iraq and Afghanistan from terrorists and their state sponsors.

(2) Al Qaeda’s ongoing and very active efforts to acquire nuclear, chemical and biological weapons, most recently Al Qaeda in Yemen’s efforts to produce the pathogen ricin.

(3) The grave nuclear proliferation threats embodied in North Korea and Iran; and...

(4) China’s and Russia’s continuing assertive and even belligerent diplomatic offensives and the build-ups in their respective conventional and strategic weapons forces.

However important it is to restrain federal spending -- and it is more important now than in living memory -- it is not the time to skimp on defending America. September will be a critical month.

Former U.N. Ambassador John Bolton, is a Fox News contributor and a senior fellow at the American Enterprise Institute, is the author of "Surrender Is Not an Option: Defending America at the United Nations" (Simon & Schuster, 2007).