The Pentagon believes Tehran is five to eight years away from being able to build a nuclear bomb.

Of course, this is the same Pentagon that said Iraq had weapons of mass destruction along with the capability to launch them against the United States.

The predicted five-year window may be a smokescreen to provide the Bush administration with a justification to launch air strikes to cripple Tehran's atomic program.

Other Pentagon sources, however, claim the five-year timeline underestimates Iran's determination to build a bomb as quickly as possible.

A Pentagon spokesman said the U.S military never comments on contingency planning.

"The United States government has been very clear about its approach to dealing with Iran. The president and the State Department are working diligently with the international community to include organizations like the IAEA (International Atomic Energy Agency) and the United Nations to address diplomatically the troublesome activities of the Iranian government," Air Force Maj. Patrick Ryder, said in an e-mail response to Reuters.

The U.N. Security Council has given Iran a Thursday deadline to stop enriching uranium, a process that can yield fuel for nuclear bombs or power plants, or face possible sanctions.

Bush has called for a swift response if Iran does not meet the UN deadline.

The United States and other major powers have accused Iran of trying to make a nuclear bomb. Tehran insists it will not halt its nuclear activities, which it contends are to generate energy.