Senate Republicans plan to call for a congressional commission to investigate the conclusions of the new National Intelligence Estimate on Iran and the specific intelligence that went into it, according to congressional sources.

The move, which would be the first formal challenge to the NIE, comes amid growing backlash from conservatives and neoconservatives unhappy about the assessment that Iran halted a clandestine nuclear weapons program four years ago.

It reflects how quickly the NIE has become politicized, with critics even going after the analysts who wrote it.

Sen. John Ensign (R., Nev.) said he planned to introduce legislation next week to establish a commission modeled on a congressionally mandated group that probed a disputed 1995 intelligence estimate on the emerging missile threat to the United States over the next 15 years.

"Iran is one of the greatest threats in the world today. Getting the intelligence right is absolutely critical, not only on Iran's capability but its intent," he said in an interview.

Ensign's proposal calls for Senate leaders to put an equal number of Republicans and Democrats on a panel to study the NIE and report back in six months.

"There are a lot of people out there who do question [the NIE]. There is a huge difference between the 2005 and 2007 estimates," he said.

The 2005 intelligence estimate reported that Iran was still working on a clandestine military program. The new assessment basically says the previous judgment was wrong on a key point.

"If it's inaccurate, it could result in very serious damage to legitimate American policy," said Sen. Jeff Sessions (R., Ala.). As recently as July, he noted, intelligence officials said in congressional testimony that they had a high degree of confidence that Iran was intent on developing the world's deadliest weapon.

While other NIEs have been the subject of intense criticism - most recently the 2002 assessment on Iraq's program to develop weapons of mass destruction - critics of the new assessment are modeling their response after the clash over a 1995 NIE on ballistic-missile threats.

That document concluded that no country other than the major declared nuclear powers "would develop or otherwise acquire a ballistic missile over the next 15 years that will threaten the contiguous 48 states or Canada."

President Bill Clinton used that NIE to veto a fiscal 1996 defense-authorization bill that would have required the deployment by 2003 of a missile-defense system capable of defending all 50 states - a project costing tens of billions of dollars.

But a congressionally mandated commission, headed by Donald H. Rumsfeld, who would become President Bush's defense secretary, concluded in 1998 that the United States "might have little or no warning before operational deployment of a ballistic missile by a hostile Third World country."

The commission's conclusions formed the basis for the Bush administration's push for a missile-defense system.

Although administration officials say they are very comfortable with the intelligence that produced the new NIE, conservative commentators challenge its veracity.

Norman Podhoretz, a commentator who has advocated air strikes on Iranian sites, said he did not believe the NIE was "very credible because it is a 180-degree turn in two years based on new discoveries. I don't see any strong reason why in two years they won't reverse themselves."

Senate Divided on Energy Legislation

Senate Democrats

searched for a compromise on energy legislation as Republican leaders made it clear they would oppose levying new taxes on the oil industry and mandating utilities to provide more wind and solar electricity.

Democrats, needing 60 votes

to overcome a GOP filibuster, fell seven votes short, 53-42, as the Senate began considering an energy package approved by the House on Thursday. All area senators voted to close debate except Arlen Specter (R., Pa.).

Much of the legislation,

including the first increase in automobile fuel-economy requirements in 32 years, has "near universal support," said Senate Republican leader Mitch McConnell of Kentucky.

But he said the House

bill "won't become law" unless the "twin millstones of utility rate hikes and massive tax increases" are removed.

Republican lawmakers

and the White House have been most critical of $13.5 billion in taxes that would be imposed on the five largest oil companies under the House-passed measure. Senate Majority Leader Harry Reid of Nevada acknowledged the House-passed bill would require some changes.

- Associated Press