Showdown on Iran's nuclear program enters endgame

You wouldn't know it from witnessing Iranian President Mahmoud Ahmadinejad, all cocky and self-confident, as he gave a trademark bellicose speech to the United Nations this week, blaming the world's ills on Zionism, capitalism and so on. But his nation is facing international crunch time over its nuclear weapons program.

Next week, diplomats from all U.N. Security Council countries plus Germany are scheduled to sit down with Iran's chief negotiator in Geneva to see whether a deal on Iran's nuclear ambitions is possible. This will be a serious final chance as the long-simmering confrontation enters a dangerous endgame.

Ahmadinejad's recent rants that Israel's days are numbered and that the Holocaust was a "lie" only make him more impossible to believe about anything – and make it more likely that Israel will pre-emptively attack Iran's nuclear facilities if diplomatic efforts show little progress. Brandishing original construction plans for the Nazi concentration camp at Auschwitz-Birkenau, Israeli Prime Minister Benjamin Netanyahu told the U.N. Thursday that "the most urgent challenge facing this body today is to prevent the tyrants of Tehran from acquiring nuclear weapons."

An Israeli strike should be a last resort: It could trigger a huge run-up in oil prices, invite retaliation against U.S. forces in Iraq and Afghanistan, and further destabilize the already volatile Middle East. Given that Iran has built many of its facilities deep underground, an airstrike might not even succeed.

The best hope of preventing this scenario is tough international sanctions against the Iranian regime, which would be a departure from recent years when the Europeans tentatively felt out Iran as the U.S. refused to negotiate – leaving plenty of room for Iran to do its usual ducking, weaving and stalling for time.

Unlike in the past, the Security Council is closing ranks on the idea of cutting off trade to Iran of the refined oil that it depends on, if Iran doesn't stop enriching uranium by year's end. That development is crucial, because Russia and China have previously refused to endorse sanctions. Now, Russian President Dmitry Medvedev says they might be inevitable. China, which trades with Iran, has been more equivocal but rarely vetoes a U.N. resolution alone.

For all of Ahmadinejad's U.N. bluster, he's dealing from a position of weakness. His hold on power at home is tenuous; his credibility abroad is negligible. Sanctions would come at a particularly perilous time for Iran's hard-line clerics, who have the final say in all matters, including the nuclear program. They still face political unrest and sporadic street protests over June's contested presidential election. With their economy in dire straits and unemployment high, sanctions on gasoline supplies could provide fresh encouragement to the opposition.

At the same time, U.S. and Russian officials should back off the assurances they have been giving Iran that Israel won't attempt to strike Iran's nuclear facilities. Keeping the military option on the table gives the Iranians more, not less, incentive to strike a deal.