Fifty-one percent (51%) of U.S. voters say President Obama has not been aggressive enough in responding to Iran's nuclear program.

A new Rasmussen Reports national telephone survey finds that only four percent (4%) think the president has been too aggressive in dealing with Iran, while 38% believe his response has been about right.

In late June, 40% of voters said the president was not aggressive enough in supporting the reformers in Iran protesting the results of the country's questionable presidential election, but 42% said Obama's response had been about right.

Seventy-three percent (73%) of Republicans and 55% of voters not affiliated with either party say the president has not been aggressive enough in reacting to Iran's nuclear program, but 61% of Democrats say his response has been about right.

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Despite conciliatory remarks by the president as recently as last week at the United Nations, Iran has continued to make threats toward Israel and others while continuing its nuclear program. On Friday, Obama and the leaders of Great Britain and France acknowledged the existence of a previously undisclosed nuclear plant in Iran and began talking about tougher diplomatic measures against the Islamic nation.

Eighty-eight percent (88%) of voters are now at least somewhat concerned about Iran's nuclear program, with 59% who are very concerned. Only 11% are not very or not at all concerned.

Voters 40 and older are more concerned than those who are younger. Republicans are more worried than Democrats and unaffiliateds.

Eighty-two percent (82%) say Iran's nuclear program is for weapons development, up slightly from late January. Only five percent (5%) believe the Iranian government's claim that its uranium enrichment program is for peaceful energy purposes. Thirteen percent (13%) are not sure.

The new survey was taken Saturday and Sunday nights prior to Iran's announcement on Monday that it had test-fired missiles with the capability of striking Israel and U.S. military facilities in Europe and the Persian Gulf region.

Iran is seen an enemy of the United States by 70% of Americans, putting it second only to North Korea on the U.S. enemies list.

Thirty-eight percent (38%) of voters say America's relationship with Iran will be worse a year from now than it is today, up six points from June. Twelve percent (12%) say the relationship will be better, and 39% think it will be about the same.

Eighty-two percent (82%) of voters say they have followed recent news reports about Iran's nuclear program at least somewhat closely, with 50% who are following very closely. Just three percent (3%) say they are not following the news about Iran at all.

Voters have expressed growing unease with the president's handling of national security issues in recent weeks.

Obama gave a highly-publicized speech in Egypt in June, reaching out to the Muslim world. But the plurality of voters (43%) say America's relationship with the Muslim world will be roughly the same in one year as it is now. Twenty-six percent (26%) say the relationship will be better; 25% say it will be worse.

In May, 49% of Americans said the United States should help Israel if it attacks Iran. Thirty-seven percent (37%) said America should do nothing if that happen. Just two percent believe the United States should help Iran.

Just 12% of voters continue to believe that the United States should be the world's policeman.

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This national telephone survey of 1,000 Likely Voters was conducted by Rasmussen Reports September 26-27, 2009. The margin of sampling error for the survey is +/- 3 percentage points with a 95% level of confidence (see methodology).

Rasmussen Reports is an electronic publishing firm specializing in the collection, publication, and distribution of public opinion polling information.