Romney: If Obama elected, 'Iran will have a nuclear weapon'.

Republican presidential candidate Mitt Romney said Sunday that if U.S. President Barack Obama is elected to a second term in the White House, Iran would surely become nuclear, AFP reported.

"It's pretty straightforward in my view. If Barack Obama is re-elected, Iran will have a nuclear weapon and the world will change if that's the case," AFP quoted Romney as saying to supporters in Atlanta, Georgia.

"This is a president who has failed to put into place crippling sanctions against Iran. And [has failed to communicate] that it's unacceptable to America for Iran to have a nuclear weapon," he said.

Romney promised his supporters that he will speak out about military options on Iran, saying that Obama had "failed to communicate that military options are on the table."

"I will have those military options, I will take those crippling sanctions and put them into place, and I will speak out to the Iranian people of the peril of them becoming nuclear," AFP quoted Romney as saying.

Romney, the frontrunner of Republican contenders for the presidential seat, has won in eight U.S. states thus far.

Meanwhile on Sunday, Obama spoke before the pro-Israel lobby group AIPAC, and insisted that all options remain on the table to prevent a nuclear Iran.

"We all prefer to resolve this issue diplomatically," Obama said in an address in Washington. "Having said that, Iran’s leaders should have no doubt about the resolve of the United States, just as they should not doubt Israel’s sovereign right to make its own decisions about what is required to meet its security needs. I have said that when it comes to preventing Iran from obtaining a nuclear weapon, I will take no options off the table, and I mean what I say."

Obama and Prime Minister Benjamin Netanyahu are due to meet at the White House's Oval Office on Monday, and expected to further discuss the Iranian issue.