Sen. Barack Obama claims that a "history of weak sanctions" on countries like North Korea and Iran has created "this slow drift towards nuclear weapons becoming a fact of life."
Obama, D-Ill., told ABC News' Charlie Gibson that as president he would "sound the alarm" about the danger of Iran's nuclear ambitions.
"If Iran gets a nuclear weapon, it triggers a potential arms race, a nuclear arms race in the Middle East, that is not only life-threatening to Israel but it is a profound, a game-changing shift when it comes to our national security," he told Gibson.
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The Democratic presidential candidate said he would not take military options against Iran "off the table," but said it would be difficult for a military strike to wipe out the rogue nation's nuclear facilities.
"Iran is a big country. They have dispersed their nuclear capabilities in a way that you're not going to see smooth, surgical strikes solving the problem entirely the way that Israel was able to deal with Iraq's nuclear threat. And so what we have to do is avoid that choice by applying the tough diplomacy that makes the calculus for the Iranians different," he said.
Obama was referring to Israel's 1981 aerial strike that demolished Iraq's Osirak nuclear reactor while it was still under construction.
Delicate Diplomacy Between Israel and Iran
Obama said it was understandable that Israel, which has threatened to bomb Iran's nuclear infrastructure, is wary of more negotiations and sanctions against Iran.
"We have a history of weak sanctions, weak inducements, that the Iranians ignore and the North Koreans before them ignored. And so we have this slow drift towards nuclear weapons becoming a fact of life," he said.
North Korea has entered negotiations with the United States and other countries to end its nuclear arms production but has not yet surrendered its nuclear arsenal.
"We've got to get serious about tough sanctions," Obama said.
Obama made his comments as he wrapped up the Middle East leg of a weeklong tour that will now move on to Europe.
The Trust Test
Obama's tour has a dual purpose: showcasing Obama on the world stage and easing doubts about his experience at home.
In a recent ABC News/Washington Post poll, 72 percent of Americans -- even most Democrats -- say Sen. John McCain, R-Ariz., would be a good commander-in-chief of the military.
Perhaps even more urgent for the Obama camp, fewer than half -- 48 percent -- say Obama would be a good commander-in-chief, a significant weakness on this measure.
He acknowledged to Gibson that polls suggest Americans, and Israelis, are wary of his commitment to Israel's security.
"Well I think that, because I'm relatively new to the international scene and because the stakes are so high, for Israel and those who are friends of Israel, people understandably want to lift the hood and kick the tires," he said.
His newness to the international scene was apparent earlier this month when he told the Israeli lobby AIPAC that he was determined that Jerusalem remain the capital of Israel, "and that it must remain undivided."
Those are explosive comments in the region since the Palestinians want East Jerusalem to the capital of a future independent state.
"I said immediately after the speech that that word was poorly chosen," he told Gibson.
Obama rejected Gibson's suggestion that using the phrase was a "rookie mistake."
"I wouldn't say rookie mistake. I think that veterans make mistakes as well," he said.
When pressed on whether he believed Jerusalem should be divided between Palestinians and Israelis, Obama said, "I think that it is going to have to be one of those final status decisions that are going to be made by Palestinians and Israelis."
ABC News' Gary Langer contributed to this report.