In a previously unannounced visit, the U.N. nuclear watchdog agency chief will visit Iran this week to help persuade the Tehran regime to meet an Oct. 31 deadline to prove it is not producing atomic weaponry, the agency said Monday. In a statement, the agency spoke of "important questions that are still outstanding," about the nature of Iran's nuclear program - wording that suggested that Tehran was not forthcoming with information needed to dispel suspicions about its activities. It was unclear how long the trip by IAEA Director General Mohamed ElBaradei had been planned, but agency officials had in recent weeks said a visit to Tehran was not on the schedule before the Oct. 31 deadline. The IAEA has been pressing Iran to prove it is not producing nuclear weapons as the United States strongly suspects. Iran has protested the deadline - agreed on by the agency's board of governors - and said its nuclear program is to generate electricity as its oil reserves decline. Failure to satisfy the IAEA, whose board of governors will meet again on Nov. 20 to assess the Iranians' compliance, would result in Iran being referred to the U.N. Security Council, which could impose sanctions. In recent weeks, Iran has twice confirmed that particles of weapons-grade uranium had been found in separate places in the country. The government said the particles came from imported nuclear equipment that had been contaminated. Ali Akbar Salehi, Iran's senior delegate to the IAEA, said earlier this month that the IAEA representatives had reached "total agreement" with Iran on measures to prove the country's nuclear program is peaceful. Iran has agreed to provide the IAEA with a list of imported equipment it contends had been contaminated. But diplomats familiar with the progress of the agency's work have recently indicated foot-dragging on the part of Tehran and said time is running out for Iran to meet the Oct. 31 deadline. ElBaradei will urge Iranian officials "to provide ... all the remaining information required to clarify important questions that are still outstanding about Iran's nuclear programs," said the agency statement. It did not offer details about his itinerary, but diplomats familiar with the agency said ElBaradei planned to leave for Tehran Wednesday and was expected back before the weekend. Iran is a signatory of the Nuclear Nonproliferation Treaty, which bans the spread of nuclear weapons. Pierre Goldschmidt, an IAEA deputy director general, and another top agency official held two days of talks in Tehran earlier this month. An IAEA inspection team is also in Tehran to carry out routine inspections of Iran's nuclear facilities. **PHOTO CAPTION*** U.N. nuclear watchdog chief Mohamed ElBaradei. (Photo by Herwig Prammer/Reuters)