By Steve Holland
WASHINGTON (Reuters) - U.S. Republican presidential candidate Rudy Giuliani said on Friday Iranians need to realize "America will not allow them to become a nuclear power" and criticized Democrats for opposing President George W. Bush's tough stance on Iran.
But Giuliani came under fire from Mitt Romney, a rival for the Republican nomination, who said the former New York mayor lacked conservative principles and is more like front-running Democrat Hillary Clinton.
Bush's decision to declare Iran's Revolutionary Guard a supporter of terrorism and to impose new sanctions continued to reverberate on the campaign trail, where Iran is competing with Iraq as a major issue in the run-up to the November 2008 election.
Giuliani, speaking in Midland, Texas, where Bush used to live, sided with the president's policy and said Democrats seem to be slamming it because "no matter what the president says they would criticize it."
Giuliani said he hoped sanctions would work "but the military option is not off the table and the Iranians should understand that, that America will not allow them to become a nuclear power."
"Their regime is too irresponsible. The world would be in too much danger," he said.
On the Democratic side, former North Carolina Sen. John Edwards again skewered Clinton for having voted for a Senate resolution that recommended the State Department declare Iran's Revolutionary Guard a terrorist organization, a vote that preceded Bush's move by several weeks.
"When Senator Clinton voted to declare Iran's Revolutionary Guard a terrorist organization, she only aided and abetted George Bush and Dick Cheney's march to war," Edwards said.
Another Democratic candidate, Illinois Sen. Barack Obama, has made similar charges against Clinton. Clinton says her vote was aimed at encouraging diplomacy in dealing with Iran, not war, and in a memo sent to reporters, the New York senator's campaign took aim at Obama.
"Stagnant in the polls and struggling to revive his once-buoyant campaign, Sen. Obama has abandoned the politics of hope and embarked on a journey in search of a campaign issue to use against Sen. Clinton," the memo said.
Many Republican strategists have been baffled by Giuliani's resilience in leading national polls for his party's presidential nomination, despite positions in favor of abortion rights and gay rights, stances traditionally out of step with the party's conservative base.
Romney, speaking to an Iowa Public Television program, tried to isolate the former New York mayor, describing him as "alone" on one side, while a group of as many as six Republican candidates stand "on the other side" -- including Romney himself.
He predicted conservatives will eventually choose one of his group and then Giuliani will face a more challenging time, "because I do believe that the Republican Party ... is not going to keep Hillary Clinton out of the White House by acting like Hillary Clinton. We have to be distinct. We have to act like Republicans."
Giuliani spokeswoman Maria Comella fired back.
"This sounds like sour grapes from Mitt Romney as he watches the mayor's lead grow and his own numbers in the states drop," she said.
(Additional reporting by Kay Henderson in Des Moines)