Brussels - The European Union renewed pressure on Iran on Friday by urging co-operation over its controversial nuclear programme and demanding the "prompt release" of EU citizens held in custody.

"The European Council reaffirms its grave concern over the development of Iran's nuclear programme and Iran's persistent failure to meet its international obligations," EU leaders were set to say in a joint statement following a summit in Brussels.

The document drafted by the 27-member bloc urged Iran to "rebuild confidence in the exclusively peaceful nature of Iran's nuclear programme," and voiced concerns over the construction of a second nuclear enrichment plant near the city of Qom.

The text also called for the "unconditional release" of European citizens put on trial in Iran, after a British embassy employee in Iran was sentenced for allegedly stirring up political unrest.

On Thursday Sweden, the current holder of the European Union presidency, criticized as "unjustified and harsh" a four- year prison term given to a British embassy employee in Iran.

The EU leaders also criticized human rights breaches in Iran, and said they were "deeply concerned" about the use of the death penalty and the violent suppression of dissent.

The EU statement came after Iran demanded amendments to an IAEA proposal designed to reduce Iran's enriched uranium stock and build confidence in its nuclear intentions.

Nevertheless, Iran said it was principally in favour of the proposal, under which Iran would ship enriched uranium to Russia and France for further processing into fuel for a medical-purpose reactor in Tehran.

Britain, France and Germany are part of the so-called 5+1 group of countries conducting negotiations with Iran over its nuclear enrichment programme, which Iran insists is for purely peaceful purposes. (dpa)