Iran offered on Tuesday to start serious talks over its nuclear programme but there was no sign it had agreed to a key U.N. Security Council demand that it freeze uranium enrichment by August 31 or face the prospect of sanctions.

"It is a very long, complex document and we are studying it," Douste-Blazy told France 2 television.

"In a few days, along with our European, American, Russian and Chinese partners we will say what we think and what we will do at the U.N. Security Council," he added.

The five permanent U.N. Security Council members Britain, China, France, Russia and the United States, plus Germany, offered Iran incentives to stop enrichment and Douste-Blazy indicated there was no room for manoeuvre on that point.

"What I know is that the resolution 1696 ... tells Iran it must stop all uranium enrichment by August 31," Douste-Blazy said.

Iran has said it will not abandon what it calls its right to enrich uranium for use in nuclear power stations. Western countries fear Iran wants to master enrichment to give it the ability to make atomic bombs.