Iran and six world powers resume nuclear talks Monday no closer to progress than in previous rounds, and with the clock ticking on international diplomatic efforts to persuade Tehran to curb activities that could be used to make atomic arms.
Diplomats from several nations meeting with Iran in Moscow depict the talks as crucial. They say it will likely be the last in a series and that, if negotiators fail to make headway in persuading Tehran to stop higher-grade uranium enrichment, it's unclear if or when new talks would occur.
Iran insists all of its nuclear activities are peaceful. It denies interest in the nuclear weapons application of uranium enrichment, insisting it wants to make only reactor fuel and medical isotopes.
While Iran wants the other side to recognize its right to enrich and blink first by easing sanctions, the six say the onus is on Tehran to show it is ready to compromise. Such a stalemate makes the chances of substantial progress unlikely in Moscow.
The United States and its Western allies routinely warn that time is running out for a diplomatic solution to the standoff. But this time such warnings carry more weight than before both for Iran and its negotiating partners _ the U.S., Russia, China, Britain, France and Germany.
Iran would be most immediately hurt by a lack of progress in Moscow followed by a long hiatus in new negotiations.
In addition to longer-term U.N. and other sanctions, Tehran is now being squeezed by a widening international embargo on its oil sales, which make up more than 90 percent of its foreign currency earnings. It desperately needs those sanctions lifted, but the six say it needs to make the first move on cutting back on uranium enrichment.
The White House also stands to lose.
Failed talks at Moscow with no immediate prospect of new meetings would almost certainly expose President Barack Obama to criticism of weakness in dealing with Iran from Republican presidential candidate Mitt Romney _ and from Israel, which has threatened to attack the Islamic Republic's nuclear installations should diplomacy fail.
It is unclear if the Jewish state would actually make good on such a threat and, if so, when. But any military move would likely draw in the U.S., widen the conflict through much of the Mideast and further hobble countries already in economic tailspin by driving oil prices sky-high.
All that should be avoidable, considering that each side is keenly interested in what the other has to offer.
Western nations in particular are eager for Iran to stop enriching uranium at a level just a few steps from weapons-grade material.
Western nations also want Fordo, the underground Iranian facility where most of this enrichment is taking place, shut down and Iran to ship out its higher-grade stockpile. Fordo is of special concern because it might be impervious to air attacks _ a possible last-resort response to any Iranian bomb in the making.
Iran, in turn, wants sanctions lifted, particularly those eroding its oil sales.
Sanctions levied by the U.S. have already cut significantly into exports of Iranian crude _ from about 2.5 million barrels a day last year to between 1.2 and 1.8 million barrels now, according to estimates by U.S. officials. A European Union embargo on Iranian crude that starts July 1 will tighten the squeeze.
Iran denies it is hurting from the oil penalties, but in India last week, U.S. Secretary of State Hillary Rodham Clinton said the sanctions are "sending a decisive message to Iran's leaders."
"Until they take concrete actions to satisfy the concerns of the international community, they will continue to face increasing isolation and pressure," she said.
Like canny chess players unwilling to expose their king, both sides have been waiting for the other to make the first move. But too long a wait could translate into opportunity missed.
"Having accumulated precious assets that bolstered their hand in negotiations, both parties are now loath to use the leverage they sacrificed so much to acquire," the Brussels-based International Crisis Group said of the standoff.
The West insists that Iran is in the wrong by continuing to enrich uranium despite U.N. Security Council demands it stop doing so. Iran says its right to do so for peaceful use is enshrined in the Nuclear Nonproliferation Treaty.
Repeating Iran's mantra, Ayatollah Ahmad Jannati, a senior Iranian cleric, said curbing uranium enrichment was not on the table.
"The Iranian nation has withstood years of Western pressure and sanctions for the realization of its nuclear energy rights and it will not give them up now," state TV quoted him as saying during Friday prayers in Tehran.
Others are more conciliatory, reflecting the many and ever-changing voices of Iran on the nuclear issue.
The talks are being convened by EU foreign policy chief Catherine Ashton, and diplomats say Iranian chief nuclear negotiator Saeed Jalili told her Monday that Iran was ready to discuss enrichment in Moscow. On Saturday, Iranian President Mahmoud Ahmadinejad told the German daily Frankfurter Allgemeine that his country is ready for "a positive step if the other side also takes steps."
But the problem of who takes the first step remains _ along with whether that will be big enough to be followed by others.
The six are coming to Moscow prepared to ease restrictions on airplane parts for Iran's outmoded, mostly U.S.-produced civilian fleet and are offering technical help with aspects of Iran's nuclear program that cannot be used for military purposes.
While not budging on lifting existing sanctions or those already decided upon, diplomats familiar with the talks told The Associated Press the six are also prepared to guarantee that no new U.N. penalties will be enacted if Tehran shows enough compromise. The diplomats demanded anonymity because that possible offer has not yet been formally made.
Washington has warned Tehran of the alternatives should it not be willing to meet the six powers' demands.
"The window for diplomacy is not indefinite," a senior U.S administration official told AP. "There is tremendous international unity and (oil) sanctions will continue to ratchet up come the beginning of July when our bilateral ones and the EU's come into full force.
"So, these, too, can serve to affect Iran's calculus and make them willing to finally meet its international obligations. The onus is on Iran to take concrete steps or it will face mounting pressure and isolation."
But the proposals from the six that already are on the table fall short of what Iran says it seeks, at least publicly _ a move to ease pressure now by easing existing or looming sanctions.
"Temporary suspension of 20 percent enrichment in return for plane spare parts is like swapping gold for chocolate. It's a joke," said Esmaiel Kowsari, a member of the Iranian parliament's National Security and Foreign Policy Commission who often speaks on the nuclear issue.
"Effectively, the West wants Iran to surrender in Moscow. That will never happen."
Associated Press writers Bradley Klapper in Washington and Vladimir Isachenkov in Moscow contributed.