EU Foreign Ministers have called on Iran to urgently allow UN inspectors into all sites suspected of being used in the production of nuclear weapons.
The move comes amid mounting pressure on Iran from the United States, and follows a series of pro-democracy protests in the capital Tehran.
However, Iran has confirmed it will not sign up to the inspections and has insisted that a ban on the country's access to nuclear technology will have to be lifted before it can agree to such a move.
Earlier, Iran protested to the US over what it called blatant interference in its internal affairs.
The move comes after the US President, George W Bush, praised almost a week of pro-democracy protests in the Iranian capital, Tehran.
Mr Bush described the demonstrations as the beginnings of people expressing themselves towards a free Iran.
Thousands of people demonstrated near Tehran university's main campus in a sixth night of anti-government protests.
Reports say gunshots sounded in the area but there were no reports of any casualties.
Police and armed vigilantes were again said to be out in force.
In another development, up to 250 dissidents in Iran have harshly criticised the country's clerical establishment, accusing them in an open letter of setting themselves in the place of God.
They said occupying a position of divine or absolute power is clear heresy and an affront to human dignity.
