The European Union (EU) has called for a delay in its ongoing nuclear talks with Tehran, a top Iranian official said in Tehran Wednesday.

Ali Aqa Mohammadi, top official of Iran's Supreme National Security Council, was quoted by the official IRNA news agency as saying that the EU call was made due to Iran's presidential elections in June and Britain's parliamentary elections in May.

Britain is one of the three EU countries behind the talks, together with France and Germany.

The official did not mention whether the EU call would affect the planned next round of talks to be held in London on April 29.

However, Mohammadi expressed optimism over the outcome of the future talks, saying "what today is raised as Iran's nuclear case has been a challenge between Iran and the West since the beginning of the 1979 Islamic Revolution. The challenge has now turned to a negotiation stage."

The official, meanwhile, hinted Iran would continue to exclude the United States outside the nuclear negotiations.

"Today, we are seeking for definition of a new interaction with the world except the United States," he said.

The United States has accused Iran of developing nuclear weapons covertly, a charge Tehran dismissed as "politically motivated".

Iran and the European Union (EU) have held six rounds of nuclear talks since Tehran suspended its highly sensitive uranium enrichment activities in November 2004 to "build confidence".

Iran has indicated it cannot tolerate prolonged negotiations, calling for a conclusion within months.