Secretary of State Colin Powell (search) said the United States wants U.N. sanctions imposed on Iran after the Bush administration concluded the country is on the verge of enriching enough uranium for four nuclear weapons.

The new alarms were raised after the U.N. International Atomic Energy Agency (search) circulated a classified report among member governments about Iran's nuclear program.

Powell said the United States wants the U.N. Security Council to impose economic, political and/or diplomatic sanctions against Iran because of steps he believes Iran is taking toward developing nuclear weapons.

Speaking with reporters after a daylong trip to Panama (search), Powell said the administration will push hard for the IAEA to refer the Iran issue to the Security Council for action when the nuclear watchdog group holds a board meeting Sept. 13.

Acknowledging that many board members do not favor Security Council action against Iran at this time, Powell said he will consult with Germany, Britain and France and other IAEA board members about Iran in the coming days.

"Unless there are assurances that the international community can count on, I think it's appropriate that it [the Iran case] be referred to the Security Council," Powell said.

Earlier Wednesday, Undersecretary of Satate John R. Bolton, the administration's point man on nuclear proliferation threats, said: "We view with great concern" revelations in IAEA report that Iran is about to convert 37 tons of yellow cake uranium into uranium hexafluoride gas.

Bolton said that move combined with Iran's recent announcement that it intends to test its gas centrifuges "are further strong evidence of the compelling need to take Iran's nuclear program to the U.N. Security Council."

Uranium hexafluoride is spun in centrifuges to produce enriched uranium, which in turn can be used to generate power or make nuclear warheads, depending on the degree of enrichment.

The United States will continue to urge other members of the U.N. agency's board of governors "to join with us in this effort to deal with the Iranian threat to international peace and security," Bolton said.

Another senior Bush administration official said after Bolton left for talks in Europe that Iran was positioning itself to produce 220 pounds of enriched uranium, enough for four nuclear weapons.

"You are talking serious business here," the official said in an interview in which his identity was withheld. Despite denials by Iran, he said the United States remained convinced that Iran was proceeding to develop nuclear weapons.

However, while Bolton indicated the Bush administration might move unilaterally to try to impose economic or other U.N. sanctions on Iran, there was little likelihood of such a move at least until after the IAEA board's Sept. 13 meeting in Vienna, Austria.

Democratic presidential candidate John Kerry's campaign criticized the Bush administration for going to war against Iraq on what it called discredited grounds instead of acting sooner to marshal U.S. allies to prevent Iran from developing nuclear weapons.

The IAEA report shows "a leading state sponsor of terrorism is yet another step closer to nuclear weapons capability," said Susan Rice, Kerry's senior national security adviser. "Yet the Bush administration has stood on the sidelines while this nuclear program has advanced. ... It is past time for this administration to develop a tough and effective strategy for dealing with Iran."

U.N. inspectors have been looking for evidence that Iran has a secret nuclear weapons program. Such a finding could be critical to the Bush administration's effort to gain support from the other 34 members of the agency to seek U.N. Security Council action.

Tom Casey, a State Department spokesman, said the report being circulated by the IAEA "continues to document the fact that through the past 18 years Iran has amassed a record of deception and denial about its nuclear activities."

"It will be up to the board to decide what the next steps are," Casey said.

Many of the questions the IAEA has about Iran's activities are outlined in its sixth and latest report, the spokesman said as he accused Iran of violating pledges to refrain from proliferation of nuclear technology and to "come clean" with the IAEA about its activities.

Henry Sokolski, a former Pentagon official who heads a private proliferation research group, said after reading the report that "we need to be backing the inspectors by putting much more pressure on Pakistan."

That is, Sokolski said in a telephone interview, Pakistan should clarify how much of the enriched uranium found in Iran came from Pakistan and how much was illicitly made by Iran.

Also, he said, "the problem with the IAEA isn't the inspectors, it is getting the board to confirm what the inspectors have found."