A senior US official said in Teheran on Thursday that Iran's new proposal failed to address the Islamic Republic's nuclear program, the "greatest concern" of the United States.

Iran's Foreign Minister Manouchehr Mottaki (1st R) meets with the four ambassadors of China, Russia, France and Germany, the British charge d'affaires, and the Swiss envoy representing the United States, in Teheran, Iran, Sept. 9, 2009. Iran handed over its new package of proposals to representatives of major powers involved in talks over its nuclear program on Wednesday. [Xinhua]

"It is not really responsive to our greatest concern, which is obviously Iran's nuclear program," PJ Crowley, assistant secretary of state for public affairs, said of Iran's proposal.

"As we consult with our P-5+1 colleagues, we'll be looking to see how ... ready Iran is to actually engage. And we will be testing that willingness to engage in the next few weeks," Crowley said.

The so-called P-5+1 stands for five permanent members of the UN Security Council - the United States, Britain, France, Russia and China, plus Germany.

Also on Thursday, White House spokesman Robert Gibbs criticized Iran's proposal for its failure to live up to its international obligations.

"Iran obviously has two paths that they can choose: one of those paths leads to increased international isolation if they don't take concrete steps to end their program," said Gibbs.

"I think Iran has to live up to its responsibilities and end its illicit nuclear program," Gibbs told reporters on Wednesday.

The latest remarks by senior officials of the White House and the State Department came when Iranian President Mahmoud Ahmadinejad on Monday invited representatives from a group of six world powers including the United States to Tehran for talks although he said negotiations over his country's right to a nuclear program would be off the table.

Discussions on the nuclear issue were "finished", said Ahmadinejad, who sticks to Iran's right to a nuclear program. "We will never negotiate on the Iranian nation's obvious rights," he said, adding that Iran would not halt its uranium enrichment efforts.

The United States and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of developing civilian nuclear power. Iran has denied the accusation and stressed that its nuclear program is only for peaceful purposes.

The Obama administration has warned that Iran could face harsher sanctions if it does not begin talks before the end of this month, when the UN General Assembly meets and the G20 group of industrial and top developing nations holds a summit in Pittsburgh on Sept. 24-25.

(Xinhua News Agency September 11, 2009)