Democratic presidential candidate Hillary Clinton, facing a crucial primary in Pennsylvania Tuesday, said that if she were in the White House and Tehran attacked Israel with nuclear weapons, the United States would be able to 'totally obliterate' Iran.

Interviewed on ABC's Good Morning America program, Clinton was asked what she would do if Iran attacked Israel with nuclear weapons. "I want the Iranians to know that if I'm the president, we will attack Iran," Clinton replied. "In the next 10 years, during which they might foolishly consider launching an attack on Israel, we would be able to totally obliterate them."

Meanwhile, U.S. Defense Secretary Robert Gates has said he believes Iran is "hell-bent" on acquiring nuclear weapons, but he warned in strong terms of the consequences of going to war over that.

"Another war in the Middle East is the last thing we need and, in fact, I believe it would be disastrous on a number of levels," he said in a speech he was delivering Monday evening at the U.S. Military Academy at West Point, New York.

The defense secretary said he favors keeping the military option against Iran on the table, given the destabilizing policies of the regime and the risks inherent in a future Iranian nuclear threat, either directly or through proliferation.

Gates also said that if the war in Iraq is not finished on favorable terms, the consequences could be dire.

"It is a hard sell to say we must sustain the fight in Iraq right now, and continue to absorb the high financial and human costs of this struggle, in order to avoid an even uglier fight or even greater danger to our country in the future," he said.

He added, however, that the U.S. experience with Afghanistan - helping the Afghans oust Russian invaders in the 1980s only to abandon the country and see it become a haven for Osama bin Laden's terrorist network - makes it clear to him that a similar approach in Iraq would have similar results.

Gates said the U.S. military was not organized or equipped for the kind of wars it finds itself in today. "The current campaign has gone on longer, and has been more difficult, than anyone expected or prepared for at the start," he said. "And so we've had to scramble to position ourselves for success over the long haul, which I believe we are doing."

UN investigator ends talks with Iranian officials

AlsO Tuesday, The UN atomic watchdog's top investigator ended two days of talks with Iranian officials that sought explanations of Western intelligence that suggested Iran secretly studied how to design nuclear bombs.

"The talks with (Olli) Heinonen were positive," a senior Iranian nuclear official, who asked not to be named, told Reuters after the talks.

Iranian officials had said Heinonen's visit was intended to advance cooperation between Iran and the IAEA, the UN body investigating Iran's disputed nuclear ambitions.

Iran says its nuclear program is a peaceful drive to produce electricity so that the world's fourth-largest crude exporter can sell more of its oil and gas abroad.

But it has failed to convince the West, which believes Tehran is seeking technology so it can build atomic weapons.

U.S. President George W. Bush and British Prime Minister Gordon Brown last week vowed to prevent Iran from developing a nuclear bomb, possibly by expanding sanctions.

The UN Security Council has imposed three sets of limited sanctions on Iran since 2006 because of its inadequate cooperation with IAEA investigations.

"The second day of talks with Heinonen and Iranian officials finished after five hours without any results being announced," ISNA reported without giving a source.

Heinonen raised a diplomatic stir in February with a presentation that indicated links in Iran between projects to process uranium, test explosives and modify a missile cone in a way suitable for a nuclear warhead.

Iran has dismissed the intelligence as baseless, forged or irrelevant. But the IAEA wants substantive explanations to enable it to wind up a long inquiry into Iran's secretive quest for nuclear power.

IAEA Director Mohamed ElBaradei has said the world "needs to make sure Iran did not have a weapons program."

IAEA officials stress that the intelligence details about weapons studies, many of them from a laptop computer spirited out of Iran by a defector in 2004 and handed to the United States, remain unverified but warrant thorough investigation.