PITTSBURGH: The United States, Britain, France and Germany threatened sanctions and demanded a new IAEA probe of Iran's nuclear program Friday after Tehran revealed a second nuclear enrichment plant.

"Yesterday in Vienna, the United States, the United Kingdom and France presented detailed evidence to the IAEA, demonstrating that the Islamic Republic of Iran has been building a covert uranium enrichment facility near Qom for several years," US President Barack Obama said at a news conference.

"The existence of this facility underscores Iran's continuing unwillingness to meet its obligations under UN Security Council resolutions and IAEA requirements," the US president said, flanked by British Prime Minister Gordon Brown and French President Nicolas Sarkozy.