Although a number of countries have already developed nuclear weapons, the UN is trying to limit the spread of these weapons because of the threat they pose.
Iran has signed the Nuclear Non-Proliferation Treaty which was designed to prevent the spread of nuclear weapons while allowing countries to develop nuclear facilities for peaceful purposes such as generating electrical power.
The International Atomic Energy Agency (Part of the UN) monitors whether countries are following the terms of the treaty.
In 2003, the IAEA reported that Iran had been secretly enriching uranium for the last 18 years.
This secrecy has aroused the suspicions of the Western members of the IAEA and they have called on the country to stop enriching uranium.
Iran has refused to stop claiming that it is in their national interest to create nuclear power.
Mahmoud Ahmadinejad, the country’s president, has made some very controversial statements in the past and this has led countries to believe that the uranium enrichment is not for nuclear energy but nuclear weapons.