The U.N. nuclear watchdog said on Wednesday it had held “good” talks in Iran about suspicions Tehran was seeking atomic weapons but more discussions were needed.

“We are committed to resolving all the outstanding issues and the Iranians certainly are committed too. But of course there is still a lot of work to be done and so we have planned another trip in the very near future,” Herman Nackaerts, deputy director general of the International Atomic Energy Agency (IAEA), told reporters after returning from three days of talks in Tehran.

Asked if he was satisfied with the talks, Nackaerts, who headed the six-member IAEA mission, said “Yeah, we had a good trip.” He declined to give more details.

Iran completed a “constructive” round of talks with the United Nations' nuclear watchdog on Tuesday and further meetings are planned, the semi-official Fars news agency reported earlier as U.S. intelligence chiefs said that sanctions and diplomacy still have a chance to persuade Iran to give up its nuclear program.

“Talks between Iran and the visiting team of inspectors from the International Atomic Energy Agency (IAEA) were constructive and ... the two sides agreed to continue the talks,” Fars quoted an unnamed source as saying.

The senior United Nations nuclear inspectors went to Tehran on Saturday for talks with Iranian officials on suspicions that the Islamic state is seeking atomic weapons, and to try to advance efforts to resolve the nuclear row, according to Reuters.

The West suspects that Iran’s uranium enrichment activities have military aims but Tehran says they are for peaceful electricity generation.

The Fars report said the date of future talks between Iran and IAEA had been set, but did not give details.

Western diplomats have often accused Iran of using offers of dialogue as a stalling tactic while it presses ahead with its nuclear program, and say they doubt whether Tehran will show the kind of concrete cooperation the IAEA wants.

Iran may offer limited concessions and transparency in an attempt to ease intensifying international pressure on the country, a major oil producer, they say. But that is unlikely to amount to the full cooperation that is required.

Technical and legal issues
Iran’s state-run Arabic language television channel al-Alam quoted an unnamed official as saying that only “technical and legal issues were discussed during the talks” on Tuesday, adding that the team had not visited any nuclear sites.

Some hardline Iranian students gathered in front of the country’s Atomic Energy Organization on Tuesday to protest against the IAEA inspectors’ visit, ISNA news agency reported.

Tension with the West rose this month when Washington and the EU imposed the toughest sanctions yet in a drive to force Tehran to provide more information on its nuclear program. The measures take direct aim at the ability of OPEC’s second biggest Oil exporter to sell its crude.

EU leaders agreed to implement their own embargo on Iranian oil by July and to freeze the assets of Iran's central bank, joining the United States in a new round of measures aimed at deflecting Tehran’s nuclear development program.

Iran rejected EU sanctions on its oil as “psychological warfare” and threatened to cut off oil exports to European countries before July 1 when the EU sanctions would be fully enforced.

Iranian officials have also repeatedly shrugged off the impact of sanctions, saying the Islamic state has responded by becoming more self-reliant.

The EU accounted for 25 percent of Iranian crude oil sales in the third quarter of 2011. But analysts say the global oil market will not be overly disrupted if Iran's parliament votes to turn off the oil tap for Europe.

Potentially more disruptive to the oil market and global security is the risk of Iran's standoff with the West escalating into military conflict.

Iran has repeatedly said it could close the vital Strait of Hormuz shipping lane if sanctions prevent it from exporting crude, a move Washington said it would not tolerate.

Cost-benefit approach
Meanwhile, U.S. intelligence chiefs said Tuesday that sanctions and diplomacy still have a chance to persuade Iran to give up its nuclear program as Tehran’s leaders have shown a rational “cost-benefit approach” in their calculations.

The top intelligence officials suggested that military conflict with Iran was not inevitable despite soaring tensions with Tehran and a war of nerves over the Strait of Hormuz.

“We judge Iran’s nuclear decision-making is guided by a cost-benefit approach, which offers the international community opportunities to influence Tehran,” James Clapper, the director of national intelligence, told senators.

“Iranian leaders undoubtedly consider Iran’s security, prestige, and influence, as well as the international political and security environment, when making decisions about its nuclear program,” Clapper told the Senate Select Committee on Intelligence.

He said economic sanctions were taking a toll and described a worsening rift between the Supreme Leader Ali Khamenei and President Mahmoud Ahmadinejad.

The overriding goal of Iran’s leaders remained “regime survival” and it was too early to say how economic strains triggered by a wave of tougher sanctions would affect their decisions, CIA Director David Petraeus told the same hearing.

With a run on the Iranian currency, inflationary pressures and unemployment, the sanctions were “biting” more now than ever before, Petraeus said.

“I think what we have to see now is how does that play out, what is the level of popular discontent inside Iran, does that influence the strategic decision making of the supreme leader and the regime?” he said.

The comments by spy agency leaders echoed President Barack Obama’s assessment in his State of the Union address last week, when he said “a peaceful resolution” remains possible with Iran.

During the hearing, the head of the intelligence committee, Senator Dianne Feinstein, revealed that Israel's spy chief Tamir Pardo had visited to Washington last week, amid speculation over a possible Israeli strike on Iran's nuclear facilities.

Such trips are usually secret but Feinstein mentioned Pardo’s visit at the televised hearing as she discussed how Israel views Iran's nuclear ambitions.

When asked about the likelihood of pre-emptive Israeli military action, Clapper replied that he would prefer to answer in a closed-door session but said sanctions might force Tehran to change course.

“Our hope is that the sanctions... will have the effect of inducing a change in Iranian policy toward their apparent pursuit of a nuclear capability,” he said.

“Obviously, this is a very sensitive issue right now.”

Clear sign
The head of the Defense Intelligence Agency, Lieutenant General Ronald Burgess, told senators Iran had “the capability, we assess, to temporarily close” the channel but did not elaborate.

The hearing confirmed U.S. intelligence services have not changed their view since an assessment last year. The 16 spy agencies believe Iran's leaders are divided over whether to build nuclear weapons and have yet to take a decision to press ahead.

Asked what would be a signal that Iran had decided to construct a bomb, Clapper said producing highly enriched weapons-grade uranium would be one clear sign.

In his written remarks, Clapper also said an alleged plot last year to assassinate the Saudi ambassador to the United States showed Iran might be more willing now to carry out attacks on U.S. soil.

But Iran’s actions would be shaped by perceptions of U.S. power as well as the consequences of the exposure of the alleged plot, he said.

Clapper said while the punitive economic measures were squeezing Iran, the “economic difficulties probably will not jeopardize the regime, absent a sudden and sustained fall in oil prices or a sudden domestic crisis that disrupts oil exports.”

For the second straight day Tuesday, U.S. lawmakers also unveiled proposals for tighter sanctions on Iran over its suspect nuclear program.

House Foreign Affairs Committee chairman Howard Berman and Senate Foreign Relations Committee member Robert Menendez, both Democrats, called for targeting Tehran’s energy sector and elite Islamic Revolutionary Guard Corps (IRGC).

“With Iran pursuing a menacing nuclear program while thumbing its nose at the international community, Tehran must be further isolated,” Berman said in a statement. “Iran leaves us no choice.”