Obama welcomes Iran agreement, promises vigilance Iran was always going to be one of the main stumbling blocks facing Barack Obama when he entered the White House in 2008. This weekend his decision to engage with Tehran appears to have succeeded where every US president's approach since Jimmy Carter has failed. Today that diplomacy opened up a new path toward a world that is more secure, a future in which we can verify that Iran's nuclear programme is peaceful and that it can not build a nuclear weapon. The United States and our friends and allies have agreed to provide Iran with modest relief while continuing to apply our toughest sanctions.," he said, but added a warning. If Iran does not fully meet its commitments during this six-month phase, we will turn off the relief and rachet up the pressure.