The deputy chief of the International Atomic Energy Agency (IAEA), Oli Heinonen, arrived in the Iranian capital for a two-day visit, seeking further information on the Islamic republic's nuclear program, which the West suspects entails secretly building weapons.

State-run Iranian news agency, IRNA, reported that Iranian officials and Heinonen "will assess the trend of cooperation between Iran's Atomic Energy Organization and the IAEA," without giving further details.

The agency's number two has made a series of visits to Iran, but it is his first since IAEA chief Mohamed ElBaradei's last report on Iran was issued in May, in which he accused the country of withholding key information on alleged weaponization studies.

Tehran, always insisting its atomic program is purely for peaceful energy purposes, has denied the existence of such studies and said that it had provided a complete response to the IAEA's questions.

Diplomats in Vienna, where the atomic agency is based, said Heinonen's visit was another attempt to get further clarification on the reported studies, and was not related to an incentive deal that the five permanent members of the U.N. Security Council, plus Germany, offered Iran to suspend uranium enrichment.

The "freeze-for-freeze" deal requested that Iran freeze uranium enrichment before launching discussions on a long-term arrangement that would allow it to pursue an atomic energy program. In return, Western nations would refrain from seeking tougher U.N. sanctions after three sets were imposed in the past two years.

Iran ignored an ultimatum imposed this week by the United States, Britain and France, which insisted on a clear response to their offer. Instead, Tehran said it would reply at its own pace and will not be pressured by deadlines.

While the IAEA envoy's mission is not technically linked to the incentives, they could very much be indirectly connected in terms of the effect that Iran's cooperation with the agency would have on Western countries seeking to punish the country.

Reports from Tehran indicated that Iranian officials would show maximum cooperation with Heinonen and the atomic watchdog to try to show that it is indeed cooperating with the IAEA and to establish that it does not have a secret nuclear weapons program.

Some Iranian analysts optimistically predict that Tehran will provide the agency's representative with the information he seeks, if only to weaken U.S.-led efforts to tighten the noose around Tehran's neck at the Security Council and perhaps to widen the gap between the five-plus-one nations on whether to add the sanctions pressure.

The five permanent members of the Security Council – the United States, Britain, France, Russia and China – as well as Germany, the six nations dealing with the Iranian nuclear issue, on Wednesday discussed in a conference call what to do after Iran failed to respond to the latest incentive offer.

But they appeared divided. Washington and London called for added pressure at the United Nations, while Russia and China, and to a lesser degree France, opted to keep the channels of persuasion open with Tehran before embarking on tougher sanctions.

The United States and Britain said the six powers now had "no choice" but to seek new U.N. sanctions after Iran failed to give a "clear positive response" to their offer. They said they agreed that contacts between EU foreign policy chief Javier Solana and Iranian negotiator Saeed Jalili would continue, but new sanctions will be discussed at the Security Council.

Not so, said Russia's U.N. ambassador Vitaly Churkin.

"It may well be that in the course of those discussions some members of the six raised the issue of sanctions," he said on Wednesday following their phone discussions. "But to the best of my knowledge, there has been no firm agreement or understanding or concerted work in this regard."

He added that while the five-plus-one would have "preferred a clear and positive response" from the Iranians, he seemed to indicate that the IAEA should deal with the nuclear issue at this stage, saying that progress was being made between Tehran and the IAEA.

Iranian analysts say that Tehran could pull the rug from under the feet of the United States and Britain and strengthen Russian and Chinese reluctance to pursue further sanctions, if they give something new and substantial for Heinonen to take back to Vienna.

As for responding to the incentives, the Islamic republic has made it clear it does not fear new sanctions since the first three have had little impact.

Yet, Iran is expected to reply in its own time, some predict by next week, but it is not likely to accept freezing uranium enrichment, which it sees as a legitimate right under the Non-Proliferation Treaty, before starting "serious talks" on its overall program.