The chief U.N. nuclear inspector begins another to visit to Iran on Monday, saying his “highest priority” is getting answers to allegations of military dimensions to the Iranian nuclear program.

Speaking before he left Vienna on Sunday, International Atomic Energy Agency deputy director Herman Nackaerts said he wants to see “concrete results” from his two days of talks with Iranian officials. But, he also cautioned that progress “may take a while.” Nackaerts previously led a team of U.N. inspectors to Iran in late January, but the visit was inconclusive.

U.N. inspectors want Iran to explain the findings of a recent IAEA report that cited evidence of Iranian work on the design of a nuclear weapon.

Israel and Western nations accuse Iran of trying to develop nuclear weapons under cover of a civilian energy program. Tehran says the IAEA report was based on fabrications and insists the Iranian nuclear program is peaceful.

Israel sees a nuclear-armed Iran as a threat to its existence and says military action may be needed to prevent that from happening. The top U.S. military officer, General Martin Dempsey, said Sunday an Israeli strike would be “premature” because it is “unclear” that Iran would assemble a nuclear bomb.

In an interview with U.S. television network CNN, General Dempsey also said Israeli military action “at this time would be destabilizing and would not achieve (Israel's) long-term objectives.” He said Washington believes Iranian leaders are “rational” and that the most prudent path for dealing with them is through international sanctions and diplomacy.

Israeli media said Prime Minister Benjamin Netanyahu discussed regional security threats with visiting U.S. National Security Advisor Tom Donilon on Sunday. No other details of the meeting were released.

Iranian Foreign Minister Ali Akbar Salehi said Sunday Tehran wants to resume talks with six world powers to resolve the nuclear dispute in a way that both sides can “win.” The five permanent members of the U.N. Security Council plus Germany have not held any nuclear talks with Iran since an inconclusive meeting in January 2011.

The United States and its allies have said they want Iran to prove it is serious about discussing their concerns. They also have been tightening sanctions on Iran to pressure it into stopping uranium enrichment, a process that has civilian and military uses.

Iran said Sunday it stopped limited exports of crude oil to France and Britain, in an apparent retaliation for an impending EU boycott of Iranian oil. The Iranian oil ministry said Iran also has taken steps to find other customers for the crude.

The 27-nation EU plans to stop importing Iranian oil from July 1. It accounts for about 18 percent of Iran's crude exports, the vast majority of which go to Asian countries, mainly China and India.

The biggest EU consumers of Iran's crude have been Italy, Spain and Greece.