TEL AVIV, Israel -- Iran is much closer to producing nuclear weapons than previously thought, and could be less than five years away from having an atomic bomb, several senior U.S. and Israeli officials say.
"The date by which Iran will have nuclear weapons is no longer 10 years from now," a senior official said recently, referring to previous estimates.
"If the Iranians maintain this intensive effort to get everything they need, they could have all their components in two years. Then it will be just a matter of technology and research. If Iran is not interrupted in this program by some foreign power, it will have the device in more or less five years."
The reassessment of Iran's nuclear potential is now described by Israeli officials as the most serious threat facing their country.
Senior Israeli officials say that if the program is not halted, they will be forced to consider attacking Iran's nuclear reactors, a tactic they used against Iraq in 1981, when Israeli warplanes bombed an Iraqi reactor.
"When we look at the future and ask ourselves what is the biggest problem we will face in the next decade," a senior Israeli military official said, "Iran's nuclear bomb is at the top of the list."
With a nuclear arsenal, analysts say, Iran could also try to dominate its neighbors on the Persian Gulf, including Iraq, which before the gulf war of 1991 had an advanced nuclear weapons program of its own.
Such domination, they say, could lead to Iranian control of the flow and price of oil to the West.
And if Iranian oratory is to be believed, the Islamic government would support a showdown with the Jewish state, whose very existence, it says, is an affront to the Muslim countries in the Middle East.
Reza Amrollahi, the president of the Iranian Atomic Energy Organization, has repeatedly denied that Iran is trying to build nuclear weapons. He says Iran's nuclear program is only for peaceful purposes.
But other Iranian leaders have often stated that Islamic countries must acquire nuclear weapons to counter the U.S. and Israeli arsenals.
Some of the current technology imported by Iran's civilian nuclear program can be used in a weapons program or can be upgraded covertly, Western officials say.
The acceleration of the Iranian nuclear program represents a defeat for the Clinton administration's drive to halt the spread of nuclear technology to Iran.
Iran, like Iraq, was to have been isolated by severe sanctions. But senior administration officials interviewed in Washington said their efforts had failed to halt the flow of nuclear technology to Iran.
The most active center for nuclear weapons research and production is in Bushehr, 470 miles south of Tehran, the capital.
It has two reactors under construction, each designed to generate up to 1,300 megawatts, or 1.3 billion watts, of electrical power -- about as much as the largest reactors in the United States.
So far, the Iranians have done little more than amass nuclear material and some equipment, like a neutron source reactor and an isotope separator.
They have yet to build, as the North Koreans did, a nuclear reactor that produces weapons-grade plutonium as a byproduct.