International Atomic Energy Agency chief Mohamed ElBaradei called on Iran to quickly ratify an additional protocol to the nuclear Non-Proliferation Treaty which would allow unannounced UN checks of its nuclear facilities.
"I hope they will sign it very soon," ElBaradei told reporters after talks with German Foreign Minister Joschka Fischer. "They told me last week they have taken the decison to conclude a protocol."
ElBaradei said Tehran should not delay in keeping this pledge.
"I would also hope that Iran, until they sign and ratify the protocol, acts as if the protocol is in force," he added.
"The more transparency we see in Iran, the more confidence we can create that the (nuclear energy) program is dedicated for peaceful purposes."
Fischer renewed the German government's call on Tehran to cooperate with UN authorities by giving a full account of its atomic energy program, saying it would be a "nightmare for all concerned" if Iran became a nuclear power.
An IAEA report on Iran will be presented to the agency's board of governors in Vienna September 8. Were Iran to be found in breach of its commitments, the matter could be referred to the UN Security Council, opening up the possibility of sanctions.
Asked about the crisis over North Korea's nuclear weapons drive, ElBaradei welcomed six-way talks last week in Beijing attended by the two Koreas, China, Russia and Japan and the United States on the dispute.
"I am encouraged by the six-party dialogue and hope it will enable us to reach a comprehensive settlement under which we will do a comprehensive and truthful verification in (North) Korea," he said.
On Iraq, ElBaradei said he would like to return to the country to continue inspections for atomic weapons but added he would be "surprised to discover" that Iraq had an active nuclear weapons program.
UN inspectors quit the country in March during the run-up to the US-led war to topple Iraqi leader Saddam Hussein.