"The Iranian response to our offer was received today. The document is extensive and therefore requires a detailed and careful analysis," Solana said in a statement.

"Pending this detailed analysis, I will be in contact with the different key interlocutors and will remain in open contact with (Iran's chief nuclear negotiator) Dr Ali Larijani, as we agreed on Sunday in our telephone conversation," he said.

The United Nations Security Council gave Iran until Aug. 31 to accept a proposal offered by the United States, Russia, China, France, Germany and Britain.

The six countries have called on Tehran to suspend uranium enrichment or face possible economic sanctions.

The offer also includes giving Iran access to light-water nuclear reactors, the lifting of some U.S. sanctions and help to join the World Trade Organization.

The deputy director of Iran's Atomic Energy Organization Mohammad Saeedi said Monday that Iran's reply will "give a suitable opportunity for the west to solve the nuclear dossier through negotiations."

He said the proposed package had "serious ambiguities" that need to be clarified in talks.

But he insisted that Iran's right to enrich uranium is non-negotiable.