"This is a threat posed to the region and to the world," White House spokesman Scott McClellan told reporters.

He added: "This is not a bilateral issue between the regime and the United States, this is an issue between the regime and the international community." Iran and the United States have not had direct relations since 1980, which many experts say is a big factor in the current diplomatic impasse.

Frank-Walter Steinmeier, the foreign minister of US ally Germany, recently called for direct talks between the two countries.

McClellan expressed US support for a resolution circulated by France and Britain in the UN Security Council, calling on Iran to halt its uranium enrichment program.

Meanwhile Tehran claimed Thursday it had made more progress in ultra-sensitive nuclear work, showing yet more defiance in the face of Western lobbying for tough Security Council action.

The Franco-British text, worked out in close consultation with Germany and the United States, invokes Chapter 7 of the UN Charter, which can authorize economic sanctions or even as a last resort the use of force in cases of threats to international peace and security.

Russia and China -- which both have veto powers on the Council -- appear to be opposed the text, but McClellan said the process is in its early stages.

"This is a draft resolution," said McClellan. "It's been circulated by the United Kingdom and France, and we are supportive of it."

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