DUBAI - Iran may in the future need highly enriched uranium to power submarines and other vessels, a top nuclear official was quoted as saying on Tuesday.

The comments by Fereydoun Abbasi-Davani, the head of Iran's Atomic Energy Organization, are likely to stoke Western concerns about the nature of Iran's nuclear program, as uranium enriched beyond 20 percent fissile purity is a relatively short technical step from weapons-grade.

"For now we have no plans for enrichment above 20 percent," Abbasi-Davani said, according to the Fars news agency.

"But in some cases ... such as ships and submarines, if our researchers have a need for greater presence under the sea, we must build small engines whose construction requires fuel enriched to 45 to 56 percent.

"In this case, it's possible we would need this fuel."

Iran now refines uranium to a 3.5 percent concentration of the fissile isotope U-235 - suitable for nuclear power plants - as well as 20 percent, which it says is for a medical research reactor in Tehran.

Western experts doubt that Iran, which is under a UN arms and nuclear technology embargo, has the capability to make the kind of sophisticated underwater vessel any time soon that only the world's most powerful states currently have.

But experts have said Iran could use the plan to justify more sensitive atomic activity. US nuclear-powered submarines, for instance, use uranium enriched to about 90 percent, also suitable for the explosive core of a nuclear warhead.

Iran says its nuclear program is for purely peaceful energy and medical purposes, and that it is its right to process uranium for reactor fuel under the nuclear Non-Proliferation Treaty, a global pact to prevent the spread of atomic arms.

Any move by Iran to enrich to a higher purity would alarm the United States and its allies, which suspect it is seeking to develop the capability to make nuclear bombs and want it to curb its nuclear program.

It would also further complicate diplomatic efforts to resolve the decade-old dispute, and may add to fears of a military confrontation.

Talks between Iran and world powers this month failed to yield a diplomatic breakthrough, and the United States and Israel, widely believed to be the only nuclear-armed power in the Middle East, have not ruled out military action to prevent Iran obtaining nuclear weapons.

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