Iran's top nuclear negotiator is expected to attend a security conference in Munich this weekend organizers said Friday, reversing an earlier announcement that he had pulled out. Klaus Treude, a spokesman for the Munich Conference on Security Policy, did not give reasons for Ali Larijani's decision to go ahead with his appearance. Earlier Friday, conference officials said he had canceled because of sickness. Also Friday, the UN nuclear watchdog agency suspended nearly half of the technical aid it now provides Teheran in line with UN sanctions slapped on the Islamic republic for its refusal to mothball its uranium enrichment program. Ali Larijani on Friday had reportedly canceled plans to attend the security conference, where he was expected to meet Western officials for the first time since limited UN sanctions were imposed in December. Larijani said earlier this week that "some negotiations with Western parties" were planned on the sidelines of the Munich Conference on Security Policy, where participants will include Russian President Vladimir Putin, German Chancellor Angela Merkel and new US Defense Secretary Robert Gates. "The official explanation is that he got sick," Teltschik told The Associated Press earlier Friday, and added that he did not expect anybody else from Iran to attend in his stead. "It's not so easy to replace Larijani; he has a key role in Iran." An official at the International Atomic Energy Agency also said Friday that Larijani had canceled his trip to Europe. Larijani had been expected to meet with the head of the UN nuclear watchdog agency during a stopover Friday in Vienna. The official spoke on condition of anonymity because he was not the agency's authorized spokesman. There was no immediate comment from Teheran. Larijani was to have held meetings on the sidelines of the conference with German Foreign Minister Frank-Walter Steinmeier and EU foreign policy chief Javier Solana. Those would have been his first talks with Western officials since the United Nations imposed limited sanctions on Iran in December over its refusal to halt uranium enrichment. About 40 other international officials will attend the annual meeting, now in its 43rd year. It promises a focus on NATO's role, with other topics including the Middle East peace process, the West's relations with Russia and the fight against terrorism. Some 3,500 police will be on hand to provide tight security for the conference and keep the usual throng of demonstrators away. This year, "several thousand" protesters are expected, said Claus Schreer, a protest organizer. With leaders including Ukrainian President Viktor Yushchenko and Estonian President Toomas Hendrik Ilves on hand, whose countries have recently been at odds with Russia, plus US Senator John McCain, who was sharply critical of Putin's government at last year's conference, there is also the potential for fireworks. Already, Russian Defense Minister Sergei Ivanov has taken a shot at the US administration's plan to build a missile defense system in eastern Europe, probably Poland and the Czech Republic. "The building of parts of a missile defense system near the Russian border is an unfriendly signal," he wrote in an article for Munich's Sueddeutsche Zeitung. "It harms the relations between Russia and the USA, Russia and the NATO states as well as Russia and Poland." In a parallel opinion piece in the same newspaper, McCain criticized Russia's decision to temporarily cut off fuel deliveries to Western Europe in January over a dispute with Belarus, and suggested Moscow was taking advantage of instability in the former Soviet satellites "to exert its unhealthy and often imperialistic influence on neighbor states."