With expectations from the UN Security Council on whether or not Iran will honour an April 28 deadline to halt uranium enrichment staying high, Olli Heinonen, the International Atomic Energy Agency's director of safeguards, has put off his visit, according to a diplomat close to the body.
The diplomat said the thinking behind this decision "depended on whether the Iranians currently in Vienna give the IAEA anything new."
An Iranian delegation was in Vienna this week negotiating with the IAEA on the agency's demands for Iran to suspend uranium enrichment that could be weapons-related and to co-operate fully with an over three-year-old IAEA investigation of an Iranian nuclear programme, which the United States charges hides secret atomic arms development, sources said.
Heinonen has decided not to travel to Iran after being on standby for the trip after a visit to Tehran last week by Mohamed ElBaradei, the IAEA chief, to seek a breakthrough in the Iranian nuclear issue.
Iran's enrichment programme has been highly controversial since the sensitive process could make either nuclear reactor fuel or atomic bomb material for the country.
Iran says its programme is a peaceful effort to generate electricity, but the IAEA has been renewing calls to see documents on dealings Iran had with a nuclear black market network run by Pakistani, Abdul Qadeer Kahn, known as the father of his country's atomic bomb.
IAEA boss ElBaradei briefly
visited Iran last week
The agency also wants to interview military officers who may have overseen secret work that could be nuclear-weapons related and to get more information on work Iran may have done on sophisticated P2 centrifuges, which can enrich uranium more quickly and abundantly, as well as documents it has on making uranium hemispheres that form the core of atom bombs.
The IAEA currently has an inspection team at the Iranian enrichment facility in Natanz; but the stakes are high as ElBaradei is to submit a report next week to the UN Security Council on Iranian compliance.
Washington is pushing for measures that could lead to economic and other sanctions if Iran fails to comply, but key Iranian allies and trading partners, Russia and China, are resisting such measures.