Iran decided at the last moment not to attend a regional Mideast security conference where US Defense Secretary Robert Gates is scheduled to deliver the keynote address, organizers said. The apparent snub comes amid ongoing hostility between the two powers despite recent US claims that Iran does not have an active nuclear weapons program. Iranian Foreign Minister Manouchehr Mottaki had been scheduled to attend the conference, which opens Friday night, but the Iranians changed their mind and sent no one to the gathering in Bahrain's capital. The Iranians refused to provide a reason for their last minute decision, but US officials in Washington said Gates planned to address America's standoff with Iran in his speech to the conference on Saturday. The conference, organized by the London-based International Institute for Strategic Studies, welcomed delegates from Persian Gulf nations, the United States, China, Russia, France, Britain, Australia and other countries. Organizers were informed early Friday that Mottaki "would not attend the Manama Dialogue and Iran would not send a delegation," said Kay Floyd, the conference's press officer. There was no immediate report in Iran on the changed stance, but earlier Friday, Iranian state radio had said that an Iranian representative would attend the Manama meeting - an indication Teheran had likely made the decision at the last moment. A diplomat at the Iranian Embassy in Bahrain, who spoke on condition of anonymity because he was not authorized to talk to the media, confirmed Teheran would not be sending anyone to the event. Gates is scheduled to address the conference Saturday in a speech titled, "The US and the Regional Balance of Power." His speech comes as Washington pushes for a third round of UN sanctions against Teheran despite a recent US intelligence report saying the country suspended its nuclear weapons program in 2003 and has shown no sign of resuming it. The report was a dramatic turnaround from one issued in 2005 that concluded Iran had restarted its nuclear weapons program, but US President George W. Bush has continued to push for the sanctions, saying international pressure is key to keeping the program dormant. The report also contained warnings about Iran's continued nuclear activity and said the country could produce enough enriched uranium to have a nuclear bomb by 2010-2015. During his opening speech to the conference Friday, Bahraini Foreign Minister Sheik Khalid bin Ahmed Al Khalifa urged Iran to cooperate with the international community for the sake of regional security, advising it to avoid a "confrontational" stance toward the rest of the world and to adhere to "the principles of openness and full transparency" when dealing with the UN's nuclear watchdog. "This new road to Gulf security is contingent on a Gulf where large regional powers coexist with their neighbors in a mutually beneficial set of relationships based on prosperity and respect rather than fear and domination," Sheik Khalid said. "I believe that events such as this Manama Dialogue provide a vital forum in which all states of the region and beyond can develop a better understanding and trust for each other's positions and viewpoints." Mottaki's spokesman, Mohammad Ali Hosseini, has said the report proved Washington's warnings over the danger of the Iranian nuclear program "are baseless and unreliable." The US and many of its allies accuse Iran of using its nuclear program as cover for weapons development, a claim Teheran denies. Washington has pushed through two rounds of UN sanctions against Iran and demands that Teheran suspend its uranium enrichment program, which can produce fuel for a nuclear reactor or fissile material for a bomb. Iran has continually refused, saying it has a right to pursue enrichment under the Nuclear Nonproliferation Treaty.