A new poll of 20 nations, with 62 percent of the world's population, finds that, among global leaders, President Barack Obama inspires the most confidence — while the leaders of Russia and Iran inspire the least.

Nearly two-thirds of those polled by World Public Opinion (www.worldpublic opinion.org) had confidence in Obama. On the other hand, Iranian President Mahmoud Ahmadinejad took last place, while Russian Prime Minister Vladimir Putin came in next to last.

Yet global approval ratings don't easily translate into policy results on Iran or Russia. That was apparent during Obama's Moscow trip this week.

The bearded visage of Ahmadinejad hovered like a surly ghost over the president's visit to Russia. Obama had hoped to convince Russia's leaders and public of our common interest in preventing nuclear proliferation and defeating violent extremists.

To be more precise: Facing threats from Islamists in the country's southern regions, Moscow should be worried about a nuclear Iran on its border. And if Iran refuses to halt its march toward nuclear weapons, Russia should support tougher U.N. sanctions against Tehran.

Obama made his pitch in a speech to university students at the prestigious New Economic School. If Washington and Moscow don't cooperate, he told them, global barriers to nuclear proliferation will crumble. He insisted a controversial U.S. program to build missile defenses was aimed at Iran, not at Russia — and urged Russia to take part in the program.

Yet there was no evidence that Putin — or even the more modern Russian president, Dmitry Medvedev — got the message or was willing, for example, to rescind the sale of a strategic air defense system to Tehran.

Obama's speech, which he hoped would reach a broad Russian audience, wasn't even carried on the state-controlled TV networks, which are where most Russians get their news.

Indeed, Russia was quick to recognize the tainted "victory" of Ahmadinejad. The state-controlled media compared the protests of the Iranian opposition to the "color revolutions" in Ukraine and Georgia, which Putin has decried.

Some Russian pundits speculate that Putin prefers tensions between Tehran and Washington so oil revenues will remain high; Moscow needs the money. Whatever their rationale, Russian leaders still seem more interested in poking Washington in the eye than in curbing the proliferation threat.

So, for now, Obama's chances of eliciting Russian cooperation in dealing with Tehran appear minimal. And without that cooperation, tougher U.N. sanctions may not be possible.