Iran’s president on Tuesday blamed the United States and other “big powers” for global ills like nuclear proliferation and AIDS, and he accused them of exploiting the United Nations for their own gain and the developing world’s loss. But, President Mahmoud Ahmadinejad said, time was on the side of the poor countries. “The big powers are going down,” he said at a meeting of foreign ministers of the Nonaligned Movement in Tehran. “They have come to the end of their power, and the world is on the verge of entering a new, promising era.” The movement is made up of such diverse members as Cuba, Jamaica and India, and it depicts itself as independent. But most of the more than 100 member nations share a critical view of the United States and the developed world in general.