US President George W Bush has condemned Iran over its nuclear programme, as reports say United Nations nuclear inspectors have found traces of highly-enriched weapons-grade uranium at a second site in the country.
Mr Bush said Tehran would face "universal condemnation" if it was found to be developing nuclear weapons.
"People understand the danger of Iranians having a nuclear weapon programme," he said on Thursday, referring to his talks with world leaders earlier in the week in New York.
The US president also said he would discuss the crisis the Iranian nuclear issue during his summit talks with Russian President Vladimir Putin on Friday and Saturday.
Diplomats said minute quantities of uranium were found last month at the Kalaye Electric Company on the southern outskirts of the capital, Tehran.
One of the diplomats at the International Atomic Energy Agency (IAEA) headquarters in Vienna told the BBC that it was unclear whether the weapons-grade material was produced by Iran or the result of contamination from imported equipment.
Officials from the IAEA are in Iran looking for evidence of a possible nuclear weapons programme.
Earlier this year, they found enriched uranium particles at a plant at Natanz.
The IAEA's board of governors has set a 31 October deadline for Iran to disprove US claims that it is secretly trying to make nuclear weapons.
Tehran says its nuclear programmes are peaceful and that it only wants to produce low-enriched uranium, unusable in bombs.
It says the Kalaye Electric Company site is not part of its nuclear power programme but has been used for storing equipment.
Monday saw Iran announce that it would scale back its co-operation with the IAEA in
response to the October deadline.
The decision, announced by Iran's representative to the IAEA, suggests that Tehran will co-operate only in areas covered by agreements with the agency.
In recent weeks, IAEA inspectors had been given access to sites not covered in such agreements, but only after several weeks of delays.
If Iran is declared to be in breach of the treaty banning the spread of nuclear weapons - the Nuclear Non-proliferation Treaty (NPT) - at the next IAEA board meeting in
November, the UN Security Council could be asked to get involved.
That could result in economic and political sanctions against Iran.