WASHINGTON -- President Barack Obama insisted last week that as the nation confronts record government debt and pressing economic needs at home, it cannot afford a lengthy, ambitious nation-building effort in Afghanistan -- but limiting U.S. involvement is unlikely to make much of a dent in the record federal debt.

Liberals complain the war has been a big contributor to the nation's budget problems, and are insisting some way be found to pay for the buildup.

But the wars in Iraq and Afghanistan, though they have virtually all been funded by deficit spending, are not the main reason why the publicly held national debt has more than doubled -- from $3.339 trillion to $7.709 trillion -- since the Sept. 11, 2001, terrorist attacks.

``It's a small part of the deficit,'' said Todd Harrison, fellow in defense budget studies at the Center for Strategic and Budgetary Assessments, a Washington research group.

That's not to say the war costs don't matter.

``Over the short term, we are certainly spending a large chunk of money of the wars, money that could be devoted to other priorities or for deficit reduction, at least once the economy improves,'' noted Josh Gordon, policy director at the Concord Coalition, a bipartisan research group devoted to fiscal discipline.

But over the long term, he stressed, ``Our fiscal challenges are substantially larger, and just ending the wars would not change those projections -- because they all assume peacetime budgets.''

Obama last week said he would deploy an additional 30,000 to 35,000 U.S. troops to Afghanistan. This year's expected $30 billion to $40 billion price tag for that should boost the total cost of wars in Iraq and Afghanistan past $1 trillion over the last nine years, according to the nonpartisan Congressional Budget Office (CBO).

That spending accounts for only about one-fifth of publicly held debt accumulated in that time.

National defense spending accounted for 20.7 percent of the federal budget last year. While that's higher than peacetime lows of around 16 percent in the late 1990s, it's less than the 26-28 percent annual shares between 1975, when U.S. involvement in Vietnam ended, and 1992, when first the Cold War and then the 1991 Gulf War ended.

What's driven the bulk of this decade's deficit boom has been spending growth in programs such as Medicare and Social Security. Human resources, which include those and other domestic programs, consumed 63.8 percent of the budget last year, compared to only 49 percent as recently as 1990.

The antidote to high deficits, say independent experts, is making tough choices on domestic spending and taxes.

``The purpose of a budget is to set priorities and make trade-offs,'' said Susan Tanaka, director of citizen education and engagement at the Peterson Foundation, a New York-based fiscal watchdog group.

STILL COUNTINGSince the U.S. invaded Afghanistan shortly after the 2001 terrorist attacks, CBO estimates the U.S. has spent $943.8 billion through Sept. 30, 2009, to meet war and war-related needs, and could spend another $1.6 trillion over the next decade -- no small sum, indeed.

Other estimates put the cost higher: A 2008 study by Nobel Prize-winning economist Joseph Stiglitz and Harvard University professor Linda Bilmes dubbed the conflicts the ``$3 trillion war.''