U.S. President Barack Obama says he is pleased that the United States has reached an agreement with other world powers on a U.N. draft resolution to impose tougher sanctions on Iran. <br/>Speaking on Wednesday at a joint news conference in Washington with Mexican President Felipe Calderon, Mr. Obama said the two leaders agreed on the need for Iran to uphold its international obligations or face increased U.N. sanctions. <br/>Earlier on Wednesday, Mojtaba Hashemi Samareh, a top adviser to Iranian President Mahmoud Ahmadinejad, rejected the draft resolution as "illegitimate" in interviews with Iranian state media.<br/>The draft resolution being discussed by the Security Council would be the fourth round of U.N. sanctions against Iran for its nuclear programme. The resolution includes an arms embargo, limits on Iranian ballistic missile activity, and more inspections of vessels suspected of containing cargo related to nuclear activities. <br/>Iranian Vice President Ali Akbar Salehi, who heads Iran's Atomic Energy Organization, also said on Wednesday that the U.S. and other world powers would discredit themselves if they passed what would be a fourth round of sanctions. <br/>