Washington and Brussels issued an unexpected joint statement on Iran, warning the country's leaders to live up to their international human rights obligations.
"We are particularly concerned by the potential for further violence and repression during the coming days, especially around the anniversary of the Islamic Republic's founding on 11 February," they said.
The Iranian opposition is expected to revive anti-government protests around the anniversary, raising the prospect of new clashes with the security forces.
Opposition supporters and security forces have clashed repeatedly since President Mahmoud Ahmadinejad won disputed elections in June. Many protesters have been rounded up and put on trial.
"The large-scale detentions and mass trials, the threatened execution of protesters, the intimidation of family members of those detained and the continuing denial to its citizens of the right to peaceful expression are contrary to human rights norms," the EU-US statement said.
"We call on the Government of Iran to live up to its international human rights obligations, to end its abuses against its own people, to hold accountable those who have committed the abuses and to release those who are exercising their rights."
Meanwhile, Iran notified the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, it planned to produce 20%-enriched uranium inside the country, angering Western powers.
The French and US defence ministers jointly announced later in Paris that the two countries would work together for new sanctions against Iran over the nuclear issue.
Robert Gates, US secretary of defence, said, "if the international community will stand together and bring pressure to bear on the Iranian government, I believe there is still time for sanctions and pressure to work".
Karl Theodor Zu Guttenberg, German defence minister, said, "those involved, especially on the Iranian side, should really think whether they want to reach a solution, and whether they should, which will have a positive effect on the country. The UN Security Council is responsible for international security and should observe this responsibility, and from that the necessary steps should follow."
On 7 February, Italy and the United States vowed to cooperate in raising international pressure on Iran to halt its nuclear enrichment programme. But defence ministers dismissed the possibility of military intervention in Iran.
(EurActiv with Reuters.)
