U.S. spy agencies see Iran pushing atom bomb research

By Adam Entous

WASHINGTON (Reuters) - U.S. spy agencies updating intelligence on Iran see growing evidence that Tehran has pushed forward with nuclear weapons research but has yet to relaunch its atomic bomb program in full, U.S. officials said.

Analysts from across the U.S. intelligence community have been finalizing a revised national intelligence estimate (NIE) that is expected to bring the United States more into line with its European allies about the state of Iran's nuclear program.

The key assertions of the 2007 NIE -- that Iran halted its nuclear weapon design and weaponization work, as well as its covert uranium conversion and uranium enrichment related-activities in 2003 -- have long been disputed by some European spy agencies.

U.S. officials have signaled that at least some of those 2007 assertions will require revision. But they expected nuanced rather than wholesale changes to the assessment in the new NIE, which could be completed within weeks.

"Basically, we're talking about research (resuming) -- not about the Iranians barreling full steam ahead on a bomb program," a U.S. official said on condition of anonymity.

"When you're looking at the Iranian nuclear program, nuance matters," the official added.

It is unclear if or when a declassified version of a new NIE on Iran will be released publicly.

The revised findings could help Washington make the case within the U.N. Security Council for a new round of sanctions against Tehran, which has rejected key parts of a deal to send abroad for processing most of its material that could be used to make nuclear arms.

Washington and its Western allies accuse Iran of trying to develop nuclear weapons under cover of a civilian program. Iran says the program is designed to generate electricity so it can export more of its valuable oil and gas.

NIEs summarize the consensus views of U.S. intelligence agencies.

In a declassified version of the 2007 NIE on Iran, the intelligence community asserted with "high confidence" that Tehran halted its nuclear weapons program in the fall of 2003. It further judged with "moderate confidence" that Iran had not restarted its nuclear weapons program as of mid-2007, when the NIE was completed.

Not all U.S. intelligence agencies in the 2007 review concurred completely. Two assessed with "only moderate confidence" that the program halt represented a halt to Iran's entire nuclear weapons program.

U.S. officials noted that the 2007 NIE made clear even high confidence judgments "carry a risk of being wrong," and defined moderate confidence as information that is "credibly sourced and plausible" but may not necessarily be fully corroborated.

It was not immediately clear how much weight U.S. spy agencies would give intelligence suggesting Iran did not stop its nuclear weapons program in full in 2003, or resumed some work sometime thereafter, as some European spy agencies assert.

Analysts said expanded nuclear weapons research may be a sign Tehran wants to be prepared should it choose in the future to move aggressively in the direction of pursuing a nuclear bomb.

(Reporting by Adam Entous; Editing by David Alexander and Eric Walsh)