The six countries pushing for a halt to Iran's suspected nuclear weapons program are expected to demand unfettered access to a uranium-enrichment facility within weeks.

The United States, Britain, France, Germany, Russia and China will make the demand at an Oct. 1 meeting with Iran, a U.S. government official said. The official spoke on condition of anonymity.

The countries will also push Iran to prove its nuclear program is for energy and peaceful purposes only.

Earlier this week, the United States, Britain and France said Iran is building a second nuclear fuel facility to produce enriched uranium in a mountainside near the city of Qom.

The head of Iran's nuclear program said Saturday that United Nations nuclear agency inspectors will be allowed to inspect the new nuclear fuel facility. However, Ali Akbar Salehi did not specify when inspectors will be allowed in.

Earlier Saturday, in his weekly radio and internet address, U.S. President Barack Obama warned that Iran must take action to demonstrate its peaceful intentions regarding its nuclear program, or face the consequences.

'A disturbing pattern'

"This is a serious challenge to the global non-proliferation regime and continues a disturbing pattern of Iranian evasion," 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.

At a news conference in New York on Friday, Iranian leader Mahmoud Ahmadinejad rejected accusations that his country has been keeping the facility a secret. He said his country recently informed the UN's International Atomic Energy Agency of its plans.

Uranium enrichment is a process that can be used to make fuel or nuclear weapons.

"The size and configuration of this facility is inconsistent with a peaceful program," Obama said Friday at the G20 meeting in Pittsburgh.

Ahmadinejad said the plant wouldn't be operational for 18 months, but he sidestepped a question about whether Iran had sufficient uranium to make a nuclear weapon.

With files from The Associated Press