The percentage of Americans with a positive view of France and Germany has moved up sharply since 2003, the poll said, when the two allies challenged President Bush's Iraq policy.
Thirty-one percent of Americans gave the nod to Iran as the worst enemy in polling of 1,002 adults between Feb. 6-9.
This represented an increase from 14 percent last year, and appeared to reflect growing American concern over the potential for the Islamic republic to acquire nuclear weapons.
Twenty-two percent listed Iraq as the worst enemy, the same total as a year ago.
Although Iraq has an American-backed government, anti-Americanism in the country is widespread, demonstrated in attacks by insurgents against U.S. troops.
Behind Iran and Iraq was North Korea, with 15 percent saying it was this country's greatest enemy. North Korea is considered by many to be a danger because of its threats to use the nuclear weapons it claims to possess.
The margin of sampling error for the telephone poll was plus or minus 3 percentage points.
The Gallup poll also measured whether people viewed other countries favorably or unfavorably.
Almost nine in 10 viewed Canada as "very favorable" or "mostly favorable," with Great Britain getting about the same rating.
Almost eight in 10 felt that way about Japan and Germany, almost seven in 10 felt that way about Israel, Taiwan, the Philippines, India and Mexico
France has rebounded nicely with a 54 percent favorable rating compared with only 34 percent having a favorable view just before the invasion of Iraq in 2003, which France strongly opposed. Forty percent of Americans now have an unfavorable view of France.
Like France, Germany is held in higher esteem nowadays than it was in 2003 when it joined Paris in the anti-war camp.
Seventy-nine percent of the poll respondents saw Germany in a favorable light, with only 15 percent unfavorable. Only half viewed Germany favorably in 2003.