Newly elected president Mahmoud Ahmadinejad believes that there is no need for closer economic or diplomatic relations with the United States, or Europe. Establishing diplomatic relations with the U.S. is very popular with the majority of the population, but not with the Islamic conservatives. To them, the U.S. is still the Great Satan, and must be destroyed. They say this a lot, and loudly. This is why an Iran armed with nuclear weapons is not a good thing.
Ahmadinejad also believes that Iran's nuclear power program should go forward, no matter what. This is popular in Iran, but brings Iran in conflict with the UN and European nations Iran needs help from to revive its economy. Apparently Ahmadinejad believes he can rebuild the economy with assistance from Russia and China, who are more likely to follow the money, than world opinion. Ahmadinejad believes that Iran can do well economically by concentrating on its neighbors, and Islamic nations in general. That, and "non-hostile" countries. Thus the European strategy of offering better trade deals, in return for Iran not building nuclear weapons, is no longer valid. Ahmadinejad has basically told Europe to take a hike.