The Bushehr nuclear power plant in southern I
The Bushehr nuclear power plant in southern IAFP/Mehr News/File

Iran could not produce enough highly-enriched uranium for an atomic bomb without being detected, U.S. National Intelligence Director James Clapper predicted on Tuesday, AFP reports.

While Iran has made strides in its nuclear program, "we assess Iran could not divert safeguarded material and produce a weapon-worth of WGU (weapons-grade uranium) before this activity is discovered," Clapper said in an annual report to Congress on global threats.

Iran's declared nuclear sites are subject to monitoring from the UN's atomic watchdog, the International Atomic Energy Agency (IAEA), as well as clandestine surveillance from US and other spy services.

The U.S. intelligence assessment, however, found that Iran has moved forward with its uranium enrichment efforts.

"Of particular note, Iran has made progress during the past year that better positions it to produce weapons-grade uranium (WGU) using its declared facilities and uranium stockpiles, should it choose to do so," the report said, according to AFP.

The assessment reiterated an analysis last year from intelligence agencies that Iran had not yet opted to build nuclear weapons and that the regime's policy was based on a "cost-benefit" approach.

"We do not know if Iran will eventually decide to build nuclear weapons," he said.

But because Iranian leaders put a high priority on preserving their power and would carefully weigh the risks of obtaining nuclear weapons, the United States and its allies had an opportunity to exert influence over Tehran's ultimate decision, said Clapper.

The American intelligence community also believed Iranian leaders are not seeking a direct confrontation with the United States, the report said.

Iran has held several rounds of talks with world powers regarding its disputed nuclear program. The latest meeting was held in Kazakhstan earlier this month, and Iran and world powers agreed to hold new talks.

There was no sign of a major breakthrough over Iran's nuclear ambitions in the Kazakh city of Almaty but the agreement on new meetings suggested potential for progress.

Reports published before the talks said the P5+1 group could consider easing sanctions on Iran's gold and precious metals trade, if Iran agrees to close down its underground uranium enrichment plant in Fordow.

However the six powers later watered down their offer to Iran, dropping their demand that the Islamic Republic shut down its enrichment plant at Fordow and insisting instead that Iran suspend enrichment work there and agree to take a series of steps that would make it hard to resume producing nuclear fuel quickly.

Iran admitted in the past it was moving more centrifuge machines for enriching uranium to the underground Fordow facility, which is carved into a mountain to protect it against possible attacks.

In its last report, issued February 21, the IAEA said that Iran had begun installing at its Natanz plant more advanced centrifuges to speed up uranium enrichment, a process at the heart of the international community's concerns.

Enriched uranium can be used for peaceful purposes but also, in highly purified form, in a nuclear weapon.

The IAEA report also repeated that Iran had told the agency that it expected its Arak reactor to start operating in the first quarter of 2014.

This reactor could provide Iran with plutonium, which could also go in a nuclear weapon. Iran denies seeking or ever having sought the bomb.