Iranian officials and the UN's nuclear watchdog ended four days of talks here Thursday aimed at resolving questions related to the Islamic Republic's nuclear program, state media reported. The conclusion of the talks comes a day before the United States, Russia, China, Britain, France and Germany meet in London to try to coordinate strategy toward Iran's disputed nuclear activities. The Iranian side expressed satisfaction with the discussions, which began Monday and focused on P-1 and P-2 centrifuges, which are used to enrich uranium, said a report on the Web site of Iran's state broadcasting company. The talks were the third round between the two sides to discuss the machines. "In the talks, the agency's negotiators raised their questions and ambiguities over the machines, and the Iranian side provided necessary answers and information," the Web site quoted Javad Vaeedi, head of the Iranian negotiating team, as saying. The report did not provide further details. The discussions were the latest attempt by the Vienna, Austria-based IAEA to address outstanding questions about the Iranian program, which some Western countries believe is cover for weapons development - an allegation Tehran denies. IAEA deputy chief, Olli Heinonen, headed the UN delegation. The talks in Tehran were seen as critical because they will form the basis for a progress report on Iran's nuclear activities planned for mid-November by Mohamed ElBaradei, head of the UN-affiliated International Atomic Energy Agency. In September, ElBaradei praised Iran's cooperation with the agency so far, but urged Tehran to answer all questions - including those on reported experiments that link enrichment and missile technology - before the end of the year. Speaking to the UN General Assembly on Monday, ElBaradei stressed that "Iran's cooperation and transparency, were keys" to his report on Iran's nuclear program. Centrifuges are used in enriching uranium, a process that can produce either fuel for a nuclear reactor or the material for a warhead. P-2 centrifuges are more sophisticated, consume less electricity and produce more enriched uranium than their predecessors, the P-1 centrifuges. The United States, Britain and France are preparing to debate a third set of sanctions against the Islamic republic in response to Tehran's refusal to halt uranium enrichment. Iran has rejected two UN Security Council resolutions requiring it to halt its enrichment program.