WASHINGTON -- International inspectors have discovered that Iran hid blueprints for a powerful device to enrich uranium, in an apparent breach of Tehran£r promise last year to disclose all of its nuclear activities, officials in Austria and Washington said Thursday.

The discovery of the concealed blueprints for a state-of-the art centrifuge, which can be used to enrich uranium for civilian reactors or nuclear bombs, raised questions about whether Tehran also has bought designs for a nuclear weapon from the same black market sources, the officials said.

Even if bomb blueprints are not found, Washington will discuss with its allies whether to ask the International Atomic Energy Agency to refer Iran£r nuclear activities to the United Nations Security Council for debate, U.S. officials said. Washington has not yet decided whether to advocate international sanctions against Iran, and will await a report from the IAEA next week before deciding what course to take, they said.

The IAEA Board of Governors is scheduled to meet in Vienna, Austria, March 8-10.

¤‘his is the smoking gun,?said Henry D. Sokolski, executive director of the Washington-based Nonproliferation Policy Education Center. ¤‘hey lied -- again.?

Iran has maintained that its nuclear program has been strictly for civilian purposes. But Gregg Sullivan, spokesman for the U.S. State Department£r Near Eastern Affairs Bureau, said the American ¥Lolicy and our sentiments are based on suspicion?of the existence of an Iranian nuclear weapons program.

Although the IAEA declared last year that Iran must make a complete declaration of all its nuclear activities, the United States thinks Iran continues to operate a secret effort to build nuclear weapons.

John Bolton, the U.S. undersecretary of State for arms control, renewed the U.S. accusation Thursday at a security conference in Berlin.

¤‘here£r no doubt in our mind that Iran continues to pursue a nuclear weapons program,?Bolton said.

Over the next three weeks, Washington will discuss the severity of the Iranian issues with IAEA head Mohamed ElBaradei and European Union partners, Sullivan said.

¤†t also gives the Iranians three weeks to come up with some accounting for their behavior,?he said. ¤‘here£r time for some diplomacy here.?But a decision to seek sanctions could follow.

¤† can£s say we£qe going to charge in and go to the Security Council, but that£r always a possibility if the behavior of the Iranians isn£s demonstrating respect for the IAEA£r authority,?Sullivan said.

Independent analysts said the finding of a newer type of gas centrifuge design, called a G-2, was significant evidence of Iranian pursuit of a nuclear weapons program. Discovery of the blueprints was first reported Thursday in The Financial Times,

The G-2 centrifuge is a new model that can enrich bomb-quality uranium in half the time as the first-generation centrifuges that Iran previously admitted to having, Sokolski of the nonproliferation education center said in a telephone interview from London.

¤‘his is like saying I prohibited you from having any motorized vehicles, and you declared your motor scooter, and I discovered you had a Ferrari,?Sokolski said.

Inspectors from the International Atomic Energy Agency found the G-2 centrifuge design in Iran while comparing material that Tehran purchased to goods that Libya acquired from a ¥Nogue?proliferation network, according to several diplomats who spoke on condition of anonymity.

Abdul Qadeer Khan, a prominent Pakistani scientist and centrifuge expert, has admitted helping supply nuclear technology to Iran, Libya and North Korea. Khan was pardoned by Pakistani President Pervez Musharraf last week but his network£r activities remain under intense investigation.

The discovery of blueprints for the second type of gas centrifuge contradicted Iran£r claim that it fully disclosed the elements of its nuclear program to the IAEA last November, two of the diplomats said in telephone interviews from Vienna.

¤†t£r nothing big in terms of capability, but it certainly calls into question Iran£r good faith,?said one of the diplomats.

The discrepancy in Iran£r declaration occurred when IAEA inspectors began to compare material that the network sold to Libya with what Iran said it had obtained through middlemen.

Along with two types of centrifuges, Libya has turned over blueprints for a crude nuclear weapon that it said were obtained directly from Khan, according to the diplomats.

¤‘he inspectors have been matching up everything Libya got with what we know Iran to have,?said one of the diplomats. ¤‘he concern is, if the Iranians got everything so far, do they have a weapons design? That would be the biggie.?

Michael Levi, a nuclear physicist at the Brookings Institution, said it will be important for the IAEA to learn whether Iran used the blueprints to build any centrifuges, and if so, in what configuration. But bomb blueprints, if discovered, would pose far more serious problems, he said.

¤†f Iran has purchased bomb blueprints, then it is going to be very hard for us to verify that they£ue given them up,?Levi said. ¤‚ven if they say they£qe giving them up, how do we know there isn£s a copy??

In that case, the international community would have to take strict measures to limit Iran£r access to bomb-making materials, he said.

¤–ou have to wonder, if they would give a weapons design to Libya, then why not Iran??said Sokolski. ¤†f it was, as I believe it was, an Islamic bomb project, they had an incentive to give them a bomb design.?

Iranian Foreign Minister Kamal Kharrazi rejected charges that his country is pursuing nuclear weapons, telling reporters in Rome that Iran was prepared to answer any new questions raised by IAEA inspectors.

The IAEA board agreed in November to forgo tough measures against Iran for hiding portions of its nuclear program before, but warned that action would be taken if more surprises were found.

¤Œbviously if this is true, this is a very serious issue that must be addressed at the coming board meeting,?said a Western diplomat in Vienna.

Centrifuges spin natural uranium into enriched fissile material that can be used to fuel civilian reactors or produce atomic bombs. Iran has no civilian need to enrich its own uranium because it can easily purchase it from abroad, said Sokolski.

The nuclear proliferation network operated by Khan and his associates sold blueprints and components for two types of centrifuges developed in Pakistan from designs stolen by Khan from a European consortium in the 1970s, according to officials unraveling the transactions with Iran, Libya and North Korea.

One type was a first-generation machine called a P-1 that used an aluminum cylinder to spin the uranium gas. Later, the Pakistanis developed the P-2, which used a cylinder made from super-hard steel alloy that allowed the machine to spin faster and produce enriched uranium more efficiently.

The Libyans initially bought designs and components for the P-1 from the Pakistani network and renamed it the L-1. Later, they switched to the second design in hopes of developing a more efficient enrichment system.

Libya agreed to abandon its nuclear program last December after negotiations with the United States and Britain. As part of the deal, it turned over the records of its nuclear program and centrifuge assemblies to the IAEA and U.S. officials.

In a speech on Wednesday, President Bush said Khan£r network had arranged for P-2 components bound for Libya to be manufactured at a plant in Malaysia.

In the speech, Bush also promised a push to expand law enforcement cooperation with the administration£r Proliferation Security Initiative, which aims to interdict shipments of weapons of mass destruction before they can be delivered to rogue nations.

In an important breakthrough Thursday, the State Department announced that the United States and Liberia had signed an agreement allowing each country to board sea vessels registered to the other that are suspected of carrying illicit shipments of weapons of mass destruction, their delivery systems, or related materials.

The agreement is considered significant because Liberia has the world£r second largest registry of ships, but under international law, authorities need permission of the flag-carrier state to search vessels for suspected contraband cargo.

¤‘his agreement sends a strong signal to proliferators that the United States and Liberia will not allow the use of their vessels for the transport or transfer of items of proliferation concern,?the agency said in a statement.

One of the diplomats in Vienna said the Iranians acknowledged having the G-2 designs only after they were confronted with evidence by the IAEA inspectors. He said that the search for a possible weapons design is continuing.