DES MOINES, Iowa — The specter of U.S. military action against Syria and further intervention in the Muslim world is generating troubled and conflicting emotions throughout America.

People cite misgivings about their country’s role as “world policeman.” They express moral outrage at atrocities in a faraway nation, tempered by dismay about trying to decide who’s good and who’s bad in a sectarian slaughter. There’s a deep ambivalence about how to use American military power for good without committing the United States to another intractable war.

Those sentiments are reflected in a series of interviews conducted Friday by The Associated Press across the country and borne out in recent polling.

In town after town, Americans weary of war after a dozen years of it are expressing unease, concern, fear and often resignation.

Some adamantly oppose any U.S. action against Syrian President Bashar Assad’s government, even though the Obama administration says he used chemical weapons to kill 1,429 people, including more than 400 children. Obama said Saturday he would seek congressional approval before launching any strike.

With Navy ships in the Mediterranean Sea ready to strike, Obama said he had decided the United States should take military action, but also determined “our country will be better off” if Congress renders its own opinion.

At the same time, he challenged lawmakers to consider “what message will we send to a dictator” if he is allowed to killed hundreds of children with chemical weapons without suffering any retaliation. Lawmakers will return to session on Sept. 9.

Most are struggling to sort out conflicting hopes and anxieties. Painful lessons from Vietnam and Iraq color the conversations. Pride in America’s strength and morality often seem pitted against fears of arrogance that can lead to conflicts much easier to start than to finish.

“I think he has to do something,” Ralph Whitney of Groton, Conn., said of Obama, even if it means “stirring up a hornet’s nest.”

Opinion polls quantify the serious reservations.

An NBC News survey suggests that the Assad government’s alleged use of chemical weapons has not persuaded more people in the U.S. to support military intervention. Half of those surveyed said the U.S. should not take military action, while 42 percent said the U.S. should.