"I think you've seen by their statements that they only want to escalate the situation, that they're continuing to move forward on defying the international community," White House spokesman Scott McClellan said at a news briefing.

"It's time for the Security Council to look at what action needs to be taken for this regime's continued defiance," McClellan said.

McClellan made the remarks soon after Iran's Supreme Leader Ayatollah Ali Khamenei said on Tuesday that Iran was ready to share its nuclear technology with other countries.

"The nuclear strength of the Iranian scientists is an example of several scientific currents in Iran that are going ahead, and the Islamic Republic of Iran is ready to transfer the experience, science and technology of its scientists," Iran's state television quoted Khamenei as saying.

US Secretary of State Condoleezza Rice, who is visiting Ankara, Turkey, said on Tuesday that she was "concerned" about Iran's statement to share its nuclear technology with other countries.

"We ... have to be concerned when there are statements from Iran, as there were apparently today, that Iran would not only have this technology but also would share its technology and expertise," Rice told reporters after talks with Turkish Foreign Minister Abdullah Gul.

The United States has been demanding Iran give up its nuclear program, which, Washington claims, is a threat to regional security. Iran denies the charges, insisting its nuclear program is solely for energy purposes.

The UN nuclear watchdog, the International Atomic Energy Agency, is due to report to the UN Security Council by Friday on whether Iran is complying with UN demands.