A British soldier walks in the Nad-e Ali district of Helmand province of Afghanistan on March 25, 2010.

Public Views Iraq, Afghan Wars as Failures 

Poll finds majority of Americans see both wars as having failed. 

A British soldier walks in the Nad-e Ali district of Helmand province of Afghanistan on March 25, 2010.

A British soldier walks in the Nad-e Ali district of Helmand province of Afghanistan on March 25, 2010.

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Most Americans now believe the wars in Afghanistan and Iraq have failed to achieve their goals for the United States, according to a new poll by USA Today and the Pew Research Center.

This pessimistic outlook has important ramifications for U.S. foreign policy. If President Barack Obama seeks to use military force in other trouble spots, such as Syria or Iran, he will run into huge opposition from war-weary Americans, pollsters and political strategists of both major parties say.

On Iraq, 52 percent of Americans say the United States mostly failed to reach its objectives and 37 percent say the war mostly succeeded. In November 2011, when the last contingent of American combat troops withdrew, there was more optimism. About 56 percent said the war had mostly succeeded and only 33 percent said it had failed.

[READ: Iraq, Afghanistan and Syria Likely Snubbed in Obama's State of the Union] 

On Afghanistan, 52 percent say that war mostly failed to achieve American goals and 38 percent say it mostly succeeded. The numbers represent a shift from 2011, when most predicted the war would succeed.

"This shows that the public is more attentive to costly wars than we might expect, even when politicians try to ignore the conflicts," political scientist Christopher Gelpi, told USA Today. Gelpi, of Ohio State University, has studied public attitudes toward the wars in Afghanistan and Iraq.

Violence has been rising in both countries as the American presence has diminished.

[ALSO: U.S. Commander: 'High-Profile, Spectacular' Attacks in Afghanistan Likely to Increase]

In his State of the Union address Tuesday, President Obama portrayed himself as a peacemaker. He noted that when he took office, the United States had nearly 180,000 troops in Iraq and Afghanistan. "Today, all our troops are out of Iraq," he said. "More than 60,000 of our troops have already come home from Afghanistan....Together with our allies, we will complete our mission there by the end of this year, and America's longest war will finally be over."

What may not be over, however, are the recriminations and the negative fallout. If the situation deteriorates in one or both of those countries, and especially if either one becomes another haven for terrorists despite U.S. military efforts to prevent it, Americans are likely to turn against other military interventions in the future.

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Ken Walsh covers the White House and politics for U.S. News. He writes the daily blog, "Ken Walsh's Washington," for usnews.com, and "The Presidency" column for the U.S. News Weekly. He is the author of the new book "Prisoners of the White House: The Isolation of America's Presidents and the Crisis of Leadership." Ken Walsh can be reached at kwalsh@usnews.com and followed on Facebook and Twitter.