Hillary Clinton issued a stark warning to Iran Tuesday, warning the country would face total annihilation if it launched a nuclear attack on Israel.

Clinton's forceful rhetoric came on ABC's Good Morning America as Pennsylvania voters went to the polls. Her opponent, Barack Obama, promised a forceful response but said he wasn't interested in such "saber rattling" and said diplomacy could prevent an Iranian nuclear program to begin with.

"I want the Iranians to know, if I am president, we will attack Iran," if they launch nukes against Israel, Clinton said. "I want them to understand that. ... We would be able to totally obliterate them. That's a terrible thing to say, but those people who run Iran need to understand that."

Clinton said she hoped her stern warning would serve as a deterrent from Iran doing anything "foolish and tragic."

Obama promised a swift and forceful response to an attack on Israel by Iran, but he said the hypothetical of a nuclear attack "presupposes a failure to begin with." Iran does not have a nuclear weapon yet and the US should do everything possible to stop that, he said. Obama has said he would open diplomatic channels with Iran, but he has not ruled out the possibility of an attack on the country to prevent its acquisition of nuclear weapons.

He went on to tie Clinton's comments regarding Iran to the Bush administration's approach to the rogue regime.

"One of the things that we've seen over the last several years is a bunch of talk using words like obliterate doesn't actually produce good results," he said. "I'm not interested in saber-rattling."

This video is from ABC's Good Morning America, broadcast April 22, 2008.

Download videoTranscript via closed captions:: iran, some language recently, you said if iran were to strike israel, there would be massive retaliation. scary words. does "massive retaliation" mean you would go into iran? you would bomb iran? is that what that is supposed to suggest?

:: the question was, if iran were to launch a nuclear attack on israel. what would the response be. i want the iranians to know, if i am president, we will attack iran. i want them to understand that. it does mean that they have to look very carefully at their society, because whatever stage of development they might be in their nuclear weaponsprogram, in the next ten years during which they might foolishly consider launching an attack on israel, we would be able to totally obliterate them. that's a terrible thing to say, but those people who run iran need to understand that. because that, perhaps, will deter them from doing something that would be reckless, foolish and tragic.