The 35-nation Board of Governors of the International Atomic Energy Agency (IAEA) is expected to vote at its closed-door board session on a toughly worded draft resolution which gives Iran a last chance to prove it has been complying with the Nuclear Non-Proliferation Treaty (NPT).

The United States says Tehran has violated the treaty in its effort to develop atomic weapons secretly. Iran, which denies the allegation, could face economic sanctions if reported to the UN Security Council for breach of its NPT obligations.

Iranian Foreign Minister Kamal Kharrazi backed off from a previous threat to "review" cooperation with the IAEA if it passed the US-backed resolution, but said the board should not politicize the issue.

"America and some European countries are trying to drive the (board's) decision toward political aims," he told the IRNA news agency. "Iran desires cooperation with the IAEA and to enable this agency to make a decision based on realities."

Washington had originally lobbied for the board to report Iran to the council this week, but backed off when it saw the majority of board members wanted to give Iran one last chance and a deadline to prove it had been complying with the NPT.

Several diplomats said days of behind-the-scenes negotiations, led by France and Germany -- Washington's opponents in its failed attempt to force the UN Security Council to back the Iraq war -- brought nearly 30 nations behind an ultimatum for Iran to come clean about its nuclear plans.

Tehran's ambassador to the IAEA, Ali Akbar Salehi, told reporters repeatedly on the sidelines of the week-long board session that his country would not accept any deadlines.

"You can't impose deadlines on a sovereign country," he said.