U.S. will never allow "second Holocaust": McCain

JERUSALEM (Reuters) - Republican presidential candidate John McCain said on Monday that the United States could never allow Iran to inflict a "second Holocaust" on the Jewish people, in comments aired on Israeli TV on the eve of a visit to Israel by his Democratic rival Barack Obama.

Israel, widely believed to have the Middle East's only atomic arsenal, has described Iran's nuclear program as a threat to its existence. Israeli Prime Minister Ehud Olmert last month said it must be stopped by "all possible means."

Asked whether he would back Israel if it chose to attack Iran's nuclear facilities, McCain told Channel 2 TV:

"But I have to look you in the eye and tell you that the United States of America can never allow a second Holocaust."

McCain, trailing Obama in the polls, said he believed tougher sanctions on Iran might persuade Tehran to suspend uranium enrichment activity Western powers fear is a cover for making nuclear bombs.

"I think we Americans, joining with our European allies, can impose significant and very impactful sanctions on Iran," McCain said, hours before Obama was due to land in Israel for talks with Israeli and Palestinian leaders.

"I would hope that that would never happen. I would hope that Israel would not feel that threatened," McCain said, ruling out a face-to-face meeting with Iranian President Mahmoud Ahmadinejad who has threatened to wipe Israel off the map.

The United States, Britain, France, Germany, Russia and China have offered Iran financial and diplomatic incentives to halt nuclear activity which Tehran says is aimed solely at generating electricity.

After talks in Geneva ended in stalemate on Saturday, the six major powers gave Iran two weeks to answer calls to rein in its nuclear activities or face tougher sanctions.

(Writing by Joseph Nasr; editing by Ralph Boulton)