Sanctions and diplomacy may yet persuade Iran to give up its nuclear program, as its leaders have shown a rational "cost-benefit approach" in their calculations, senior US officials said.

Meanwhile, The chief UN nuclear inspector returned from a visit to Tehran on Wednesday saying there was still "a lot of work" to do, with Iran's foreign minister saying the team did not visit any atomic sites.

"We had three days of intensive discussions about all our priorities. We are committed to resolving all the outstanding issues and the Iranians said they are committed too," Herman Nackaerts told reporters at Vienna airport.

Iranian Foreign Minister Ali Akbar Salehi told the Fars news agency that the talks were "good" and it was agreed to continue them in the future.

The top US intelligence officials suggested that military conflict with Iran was not inevitable, despite soaring tensions with Tehran and a war of nerves over the strategic Strait of Hormuz, a key oil trade choke point.

"We judge Iran's nuclear decisionmaking is guided by a cost-benefit approach, which offers the international community opportunities to influence Tehran," Director of National Intelligence James Clapper told the US Senate Select Committee on Intelligence.

"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," hesaid.

The comments by senior intelligence official 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.