Quoting western intelligence sources, the newspaper said Ali Akbar Salehi, Iran's top diplomat on the UN nuclear watchdog, met the agency's director general, Mohamed ElBaradei, at the home of a prominent Egyptian businessman.
At the end of their two-hour discussion, the paper said El Baradei declared that his agency could not ignore evidence on Iran's nuclear programme.
ElBaradei did pledge that the facts would be presented in a moderate way, according to the German paper, which supplied no direct quotations.
IAEA spokeswoman Melissa Fleming, contacted by AFP, emphasized that no external factors were allowed to influence the agency's reports.
"We decide how we write the report," she said. "It's technical, factual and objective and there is no tone, just the facts."
The German paper said that in the report, ElBaradei observed that Iran had shown better cooperation with the agency than in the past.
According to the paper, however, he also spelled out that some of Tehran's statements about its nuclear programme had been inconsistent.
ElBaradei announced last month that UN inspectors had found traces of highly enriched uranium at an Iranian nuclear facility.
He also warned of "terrible consequences" if Iran's claim that its nuclear programme was entirely non-military turned out to be false.
The IAEA is due to turn its attention back to the issue on Monday, as Washington increases pressure for the UN Security Council to threaten Tehran with sanctions unless it agrees to surprise nuclear inspections to dispel suspicions of a covert nuclear weapons programme.