US President Barack Obama warned Iran that it must prove that its nuclear program has peaceful intentions or the country will face increased pressure and isolation.
Obama's warning came one day after he announced with French President Nicolas Sarkozy and British Prime Minister Gordon Brown that Iran admitted to the UN nuclear watchdog that it had built a second uranium enrichment facility.
Iran's secret nuclear facility to enrich uranium "is a serious challenge to the global non-proliferation regime, and continues a disturbing pattern of Iranian evasion," Obama said in his weekly audio and video address.
"That is why international negotiations with Iran scheduled for October 1 now take on added urgency," Obama said, referring to an upcoming meeting between key world powers and Iranian negotiators in Geneva.
The president said his offer to talk with the Islamic Republic on its controversial nuclear program remains open.
"My offer of a serious, meaningful dialogue to resolve this issue remains open. But Iran must now cooperate fully with the International Atomic Energy Agency, and take action to demonstrate its peaceful intentions," Obama said.
On this issue "the international community is more united than ever before," Obama said.
Iran's leaders "must now choose - they can live up to their responsibilities and achieve integration with the community of nations. Or they will face increased pressure and isolation, and deny opportunity to their own people," he said.