The negotiating stance from Iranian officials never varies: The Islamic Republic will not give up its capabilities to make nuclear fuel. But embedded in the messages are meanings that reach beyond Tehran's talks with world powers.
It points to the struggles within Iran's ruling system as it readies for the next round of talks scheduled to begin next week in Baghdad.
Iran's Islamic leadership _ which crushed an opposition groundswell nearly three years ago and later swatted back a power grab by President Mahmoud Ahmadinejad _ has now staked its political credibility on its ability to resist Western sanctions and hold firm to its rights under U.N. treaties to enrich uranium.
Any concessions _ either too great or too fast _ could risk internal rifts within Iran's power structure. And that could draw powerful forces into the mix, including the Revolutionary Guard that acts as defender of the theocracy and overseer of the nuclear program. As talks deepen, so do the political considerations for an Islamic establishment that cannot afford to appear to come away empty handed.
"Insisting on a halt to enrichment is a deal breaker," said Tehran-based political analyst Behrooz Shojaei. "It is Iran's red line."
This means smaller targets are likely necessary to keep dialogue alive after the Baghdad session next Wednesday between Iran and the six-nation group comprising the permanent U.N. Security Council members plus Germany.
A possible steppingstone goal for the U.S. and allies is to seek to halt Iran's production of uranium enriched to 20 percent levels, the highest-grade material acknowledged by Tehran. The enrichment level is far above what's needed for Iran's lone energy-producing reactor, but it is appropriate for use in medical research. It also could be boosted to weapons-grade strength in a matter of months.
Iran insists it has no interest in developing atomic weapons, but it sees its uranium labs as a mainstay of its technological advances that include long-range missiles and an aerospace program that has promised another satellite launch this month. There still could be some room, however, for bargaining.
Iran has signaled it could consider ending the 20 percent enrichment. In return, though, it wants Washington and Europe to ease some of the most painful new sanctions, including those hitting Iran's oil exports and its access to international banking networks.
Such demands would directly test the West's flexibility.
Previously, Washington and European allies have insisted that Iran must take the first step and suspend all uranium enrichment as required by several U.N. Security Council resolutions. They also are under pressure from Israel to avoid protracted give-and-take negotiations.
Last week, the European Union's foreign policy chief Catherine Ashton met with Israeli officials, including Prime Minister Benjamin Netanyahu, to discuss the upcoming talks. Later, Ashton said she hoped for "concrete" results in Baghdad.
But the semiofficial Fars news agency quoted Gen. Yadollah Javani, a Revolutionary Guard adviser, as saying it's too early to be optimistic.
"Iran does not trust the West," he said. "The West should build the trust in the long run."
Netanyahu derided the opening round of talks last month in Istanbul, mocking them as a "freebie" that gave Iran international cover to continue enriching uranium. Iran, in turn, has accused Israel of trying to destroy the negotiations as pretext to a possible military strike.
"All the sides are moving with extreme caution," said Mustafa Alani, a regional affairs analyst at the Gulf Research Center based in Geneva. "It seems no one wants to give too much or say too much at this stage. But also no one wants to be portrayed as the side that killed the talks."
This is the tricky ground being navigated by Iran.
Its leaders are desperate to avoid any impression of caving under the Western economic squeeze. Any serious rollbacks _ without Western concessions in return _ could open room for hard-liners to take pot shots at the ruling clerics. It also could put the Revolutionary Guard in the awkward position of defending the Islamic system against ultra-nationalists who normally side with the Guard.
The timing, too, brings added concerns for Iran.
Ahmadinejad is moving into his last year in office and the ruling theocracy is closely watching for any signs of an opposition resurgence before next year's elections. It took months for the Revolutionary Guard to snuff out unprecedented street protests after Ahmadinejad's disputed re-election in June 2009. Then the ruling system turned against Ahmadinejad last year after he tried to challenge the authority of Supreme Leader Ayatollah Ali Khamenei.
"Too much political capital has been invested in the nuclear program for ... Khamenei to simply slink away and retreat," wrote Iranian affairs analyst Afshin Molavi in Tuesday's edition of The National newspaper in Abu Dhabi.
Even after the feuds with Khamenei, Ahmadinejad has been a loyal advocate to Iran's negotiating positions at the talks.
"If the Westerners change their attitudes and pay respect to the Iranian nation, they will be treated respectfully by Iranians, in return," Ahmadinejad said Monday during a tour of eastern Iran.
He added: "They should know that Iranian nation will not take a single step back from their basic rights" _ a clear reference to uranium enrichment.
In Vienna, envoys from Iran and the U.N. nuclear agency held a second day of talks over suspicions that Tehran might have tested atomic arms technology at a military site. Iran denies the claims.
The International Atomic Energy Agency has sought access to the Parchin base for more than four years. It also wants to interview scientists and review documents.
The IAEA believes Iran in 2003 ran explosive tests needed to set off a nuclear charge. The suspected blasts took place inside a pressure chamber, the agency said.
A senior diplomat familiar with the IAEA probe says Iran has never said whether the chamber existed. A computer-generated drawing provided to The Associated Press by a nation critical of Iran's nuclear program shows such a structure. The official who shared it said the drawing was based on information from someone who saw the chamber.
Iranian envoy Ali Asghar Soltanieh told reporters in Vienna "everything is on the right track." He described the atmosphere as "very constructive."
Murphy reported from Dubai, United Arab Emirates. Associated Press writer George Jahn in Vienna contributed to this report.