Iranian Supreme Leader Ayatollah Ali Khamenei delivers a speech in Tehran in July. Khamenei says Western-led sanctions will not force Iran to change its policies, but there are signs of other concerned voices in Iran.

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It's ALL THINGS CONSIDERED from NPR News. I'm Audie Cornish.

It was a weekend of tough talk about Iran and its nuclear activities. There were heated words and dire warnings from Israel's prime minister and from leaders in Iran. It may appear as though international negotiations with Iran have ground to a halt. But that's not the whole story. Behind the scenes, Iran and the U.S. and other nations continue to communicate. At the same time, pressure is building on Iran in the form of an oil embargo, tough banking sanctions, and an aggressive push from United Nations nuclear inspectors.

NPR's Mike Shuster has more on the state of play.

MIKE SHUSTER, BYLINE: Yukiya Amano is frustrated. Amano is the director general of the International Atomic Energy Agency. Last week, he told a meeting of the agency in Vienna, he is frustrated with Iran's unwillingness to show the IAEA what's going on at a base called Parchin.

YUKIYA AMANO: Iran should engage with us without further delay on the substance of our concerns. We need to stop going around in circles, discussing process.

SHUSTER: Amano really wants to see what's under some plastic sheeting at Parchin, where, for months, Iranian workers have been busy taking down buildings, tearing up roads and planting new shrubs. The suspicion is that Iran engaged in high explosive tests there, the kind that might be related to a nuclear weapon.

As a result of the IAEA's frustration and the so-far unfruitful talks with the U.S., Europe, China, and Russia, there is a move to tighten further the already painful economic sanctions imposed on Iran. That was the message from British Foreign Secretary William Hague just a few days ago.

WILLIAM HAGUE: It is necessary to increase the pressure on Iran, to intensify sanctions, to add further to the EU sanctions that are already in force which are having a serious impact on Iran.

SHUSTER: Both France and Germany have echoed that sentiment.

In a recent TV appearance, President Mahmood Ahmadinejad acknowledged that Iran is hurting under the pressure.

MAHMOUD AHMADINEJAD: (Foreign language spoken)

SHUSTER: There are barriers to selling our oil, Ahmadinejad said, and there are barriers hindering the transfer of our money. But we are lifting those barriers, he said, adding it takes months to remove them.

In fact, Iran right now is exporting less than half the oil it was selling a year ago. The value of Iran's currency, the rial, continues to plummet. Last week, the rial hit 25,000 to the dollar. A year ago, it was 9,000 to the dollar. This has triggered widespread inflation and even food shortages in some places.

The sanctions are doing what they are designed to do, says Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace.

KARIM SADJADPOUR: At the moment, I think the Obama administration believes that cold gridlock is better than hot conflict. So, simply containing the situation until November is something positive.

SHUSTER: This appears to be the two prongs of the administration's strategy: engage with Iran to the extent possible through talks led by the European Union and let the oil and banking sanctions do their work until at least after the November presidential election.

If Iran is feeling the economic pain, though, the ultimate aim of the pressure is still elusive, says Karim Sadjadpour.

SADJADPOUR: The goal of the sanctions is to compel the Iranian leadership to change the nuclear calculations. And so far, there's no evidence that it's done that.

SHUSTER: One man holds the key, the Supreme Leader Ayatollah Ali Khamenei. His attitude has always been, never compromise, concessions signal weakness and invite even more pressure, says Golnaz Esfandiari, an Iran analyst at Radio Free Europe, Radio Liberty.

GOLNAZ ESFANDIARI: You know, Khamenei doesn't listen to others. He's been the ultimate decision-maker for more than two decades, and he hasn't been listening to other people.

SHUSTER: But there are indications the pressure is sparking debate. Some conservatives in the press, the parliament, and among senior officials are questioning whether the nuclear program is worth the pain.

ESFANDIARI: There is concern. Even though you hear Iranian officials saying that, you know, we've been under sanctions for 30 years or more than 30 years, and this is nothing new for us. But you hear voices of people who are concerned.

SHUSTER: Still, it is not yet clear what level of economic pain, if any, will cause Iran to rethink its nuclear activities.

Mike Shuster, NPR News. Transcript provided by NPR, Copyright NPR.