The International Atomic Energy Agency (IAEA) said on Friday that Tehran had pressed ahead with enrichment during a 30-day grace period and had not answered questions exploring whether its nuclear programme is purely civilian.
The Security Council, which received the report on Friday, could impose sanctions against Iran.
The report said questions persisted over Iranian research on advanced "P-2" centrifuges, documents on how to design an atomic bomb core, and intelligence reports of links between uranium ore processing, high-explosives tests and a missile warhead design.
"Iran was supposed to suspend [uranium enrichment], but since they continue to do experiments, they have not suspended enrichment efforts.
"The information available to us shows they have not heeded the request for compliance so far," an official close to the IAEA said.
Tehran has said its enrichment policy is irreversible and that it can withstand any consequences, whether financial penalties or military attack.
Speaking hours before the reported was submitted, the Iranian president said that no UN Security Council resolution could make Iran give up its nuclear programme.
"Those who want to prevent Iranians from obtaining their right, should know that we do not give a damn about such resolutions"
"Those who want to prevent Iranians from obtaining their right, should know that we do not give a damn about such resolutions," Mahmoud Ahmadinejad told a rally in northwest Iran on Friday.
He added that Iran was ready to defy its enemies.
"Enemies think that by ... threatening us, launching psychological warfare or ... imposing embargos they can dissuade our nation from obtaining nuclear technology.
"The Iranian nation insists on its right to peaceful nuclear technology. We will not back down one iota," he said.
However, Iran has offered to provide a timetable for co-operation with the IAEA if the UN nuclear agency, rather than the Security Council, oversaw Iranian compliance, the IAEA said.
"Iran will provide a timetable within the next three weeks" the IAEA said, if "the Iran nuclear dossier will remain, in full, in the framework of the IAEA and under its safeguards".
The report said inspector tests confirmed Iran's claim this month to have enriched uranium with a cascade of 164 centrifuges to the low level needed for fuelling nuclear power plants.
It must be purified to a much higher level to set off the chain reaction required for a bomb.
Iran is also building two new cascades of 164 centrifuges at its underground enrichment plant, which IAEA inspectors are monitoring.
"What is relevant is that they got the first 164-centrifuge cascade up and running and managed to produce low-enriched uranium," said a senior official versed with the report.
"The 164 centrifuges continue to spin as far as we know, and they are probably able to repeat the enrichment cycle at any point in time," said the official, who asked not to be named.