The United States and Europe are expected to delay a push to refer Iran's nuclear program to the United Nations Security Council for possible sanctions. Diplomats at the U.N. atomic agency say U.S. and European officials agreed to the move to give Russia more time to persuade Iran to compromise on its nuclear activities. The U.N. agency's board is set to meet in Vienna Thursday. In Washington, a State Department spokesman (Sean McCormack) said U.S. and European officials are trying to encourage Iran to return to the negotiating table. Talks between Europe and Iran broke down in August, when Iran resumed uranium conversion, sparking international criticism. The United States accuses Iran of seeking to build nuclear weapons, which Iran denies. An Iranian exile Monday accused Tehran of building an extensive network of tunnels with North Korean help to conceal nuclear weapons activities. The exile, Alireza Jafarzadeh, is a former spokesman for the National Council of Resistance of Iran -- a group designated by U.S. officials as a terrorist organization.