Female pupils listen to the Iranian president Mahmoud Ahmadinejad’s speech at parliament in Tehran on Jan. 16, 2013. Prospects for nuclear talks have grown more uncertain after Iran declined to respond to at least two proposals for meeting dates. (ABEDIN TAHERKENAREH/EPA)

Four weeks after agreeing in principle to nuclear talks, Iran has gone silent about its plans for the negotiations, baffling U.S. and European diplomats while also signaling internal discord over what analysts on both sides see as the best chance in years for a nuclear bargain with the West.

Prospects for the talks — which U.S. officials last month described as imminent — have grown more uncertain after Iran declined to respond to at least two proposals for meeting dates, Western diplomats said. Iranian and European Union officials discussed logistical issues by phone on Monday amid hopes that a meeting could still occur before the end of the month.

But with progress at a crawl, officials and analysts on both sides expressed concern that the chances for a deal were being undermined by political divisions, in Tehran as well as in Western capitals. Hard-liners in Iran have spoken publicly against making any nuclear concessions, while in the United States, conservatives in Congress have warned against a deal that would allow Iran to retain any ability to enrich uranium, even for nonmilitary purposes.

“The problem for the Iranians is not the date; it’s a worry that the meeting will not be successful,” said Seyed Hossein Mousavian, a former nuclear negotiator for Iran who lives in the United States. “They want to have a meeting as soon as possible, but they don’t want to be blamed if there’s another failure.”

The maneuvering over meeting dates and venues cast a shadow over a visit to Iran this week by officials from the International Atomic Energy Agency, the U.N. nuclear watchdog. The IAEA is prodding Tehran to grant access to military facilities where the agency believes Iran secretly conducted research on nuclear weapons a decade ago. Iran insists its nuclear program is exclusively peaceful.

Although Iran and the IAEA reported progress last month toward resolving the dispute, the agency’s chief, Yukiya Amano, told reporters that he was “not necessarily optimistic” about the outcome of the meeting. Analysts say Iran would probably preserve its bargaining chips for the broader dialogue with the group known as P5-plus-1 — the United States, Britain, China, France, Russia and Germany.

Three rounds of talks last year between Iran and the P5-plus-1 ended in deadlock. But Iranian envoys signaled a possible diplomatic thaw last month by agreeing to resume negotiations about possible curbs on the nuclear program. The news sent diplomats scurrying to pack for meetings that were expected to begin in mid-December or immediately after the New Year holiday.

But two tentative meeting dates passed without a response, prompting speculation that the Iranians were stalling for time or were locked in an internal debate over whether to agree to limits on its nuclear program in return for future sanctions relief, diplomats and analysts said.

“They’ve gone to ground,” said one senior U.S. official, speaking on the condition of anonymity to discuss sensitive diplomacy. “We’re all waiting, and everyone is checking with everyone else, but there’s been nothing at all.”

Concerns on both sides

Still, key officials on both sides continue to suggest that conditions are right for a deal, given Western anxieties about the prospect of another Middle East military conflict and Iranian anguish over unprecedented economic sanctions. In Tehran, a growing chorus of current and former officials in recent weeks has touted the need for a diplomatic end to what they see as the root cause of many of Iran’s problems.

“For the West to become confident about our peaceful nuclear activities and for us to get our rights and get past the effects of sanctions and the difficult path the enemy has prepared for us, there is only one way, and it is negotiations,” Hassan Rowhani, a former senior Iranian nuclear negotiator, told an Iranian news agency.

But in Iran, President Mahmoud Ahmadinejad’s many rivals are loath to give him space to make a settlement, which would allow him to take a measure of credit for mending relations with the United States before his final term ends in the summer.

“While the Supreme Leader has final say on the nuclear issue, the next president would at least initially be able to enter the scene with some fresh ideas and have room for maneuvering,” Iranian political analyst Mohammad Ali Shabani said in an e-mail.

In any case, Iran is unlikely to accept a deal that does not include clear timelines for sanctions relief, which would be key to gaining public support for a settlement, Iranian policy­makers and analysts say.

Mounting international sanctions have hampered Iran’s ability to sell oil abroad and transact with foreign banks. The economic ripple effects have caused shortages of food, medicine and imported gasoline, the latter of which has been replaced by low-quality fuel that is contributing to air pollution blamed for hundreds of recent deaths.

“There are sufficient forces in the Iranian society to push for change in relations, but . . . only if the United States also shows flexibility on the nuclear issue and abandons aspects of policies that have so far failed to force Iran to bend,” says Farideh Farhi, a political science professor at the University of Hawaii who specializes in Iran.

Fragmented leadership

But just who in Iran would make any decision to bend remains unclear.

Iranian foreign policy was long thought to lie solely in the hands of its supreme leader. Over time, though, the pragmatism required for Iran to grow economically, militarily and politically in an unstable region replaced many of the regime’s more fundamental tendencies and widened the field of domestic players, who often have diverging interests.

Today, with opposing political factions seeking to advance their own agendas, what is often perceived abroad as mixed signals from Iranian leaders is actually a set of competition visions for Iran’s diplomatic future.

U.S. officials still have difficulty understanding the decisions and fragmented leadership that influence Iran’s foreign policy, 34 years after diplomatic relations between Washington and Tehran were severed, analysts say.

On many occasions in the past, an agreement briefly appeared to be within reach but evaporated as opposition to a deal mounted in Iran.

The question is whether Ayatollah Ali Khamenei, Iran’s supreme leader, has both the political backing for a deal and the stomach for painful concessions, said Dennis Ross, a former top adviser to the Obama administration on Iran. Ross said he thinks the odds are not favorable.

“Does Khamenei widen his circle of decision-making so that he can take this reasonable step?” Ross asked. “I’d put it at less than 50-50.”