Vienna, Austria ? The U.N. nuclear watchdog agency said in a report Tuesday that Iran obtained documents and drawings on the black market that serve no other purpose than to make an atomic warhead. Tehran warned of an “end of diplomacy” if plans to refer it to the U.N. Security Council are carried out.

The report by the agency, ahead of a meeting of its 35-member board Thursday, also confirmed information recently provided by diplomats familiar with the Iran probe that Tehran has not started small-scale uranium enrichment since announcing it would earlier this month.

Nevertheless, the findings added to pressure to refer Tehran to the Security Council within days. Such a move, Iran said, would lead to a halt in surprise U.N. inspections beginning Saturday and prompt it to resume frozen nuclear activities.

Iranian President Mahmoud Ahmadinejad prays at the grave of the late revolutionary founder Ayatollah Khomeini, shown in the portrait, Tuesday in Tehran, Iran.

“If it happens, the government will be required under the law to end the suspension of all nuclear activities it has voluntarily halted,” Iranian Foreign Minister Manouchehr Mottaki said late Tuesday, speaking on Iranian television.

Iran insists its nuclear program is civilian only and has no other purpose than to generate power.

European and Russian officials insisted the opportunity for negotiations was not lost, even after envoys from Britain, China, France, Russia and the United States agreed to recommend that the IAEA’s board report Iran to the council.

The findings about the design obtained by Iran on the black market were contained in a confidential report for presentation to the IAEA board and provided to The Associated Press.

In the brief report obtained Tuesday, the nuclear agency said bluntly that the 15 pages of text and drawings showing how to cast fissile uranium into metal were “related to the fabrication of nuclear weapon components.”