The EU delegation is rallying support for the US
The head of the delegation, Belgian Foreign Minister Louis Michel, said that the EU and Iran's authorities were exploring ways of combating terrorism and boosting ties at the same time.
The EU officials, who have meetings with President Mohammad Khatami and Foreign Minister Kamal Kharrazi scheduled, arrived in Tehran on Tuesday from Pakistan, on the second leg of a five-nation tour of the region.
But Iran's supreme leader, Ayatollah Ali Khamenei, has made it clear that Iran will provide no help of any sort for an attack on Afghanistan.
Anti-US rhetoric
He launched a bitter attack on the United States, accusing it of being insincere and unqualified to lead a global drive against terrorism.
He said Washington was trying to exploit the current crisis to spread its influence in central Asia. "They intend to come and establish themselves in this region under the pretext of lack of
security," he said.
The ayatollah was addressing a crowd of war veterans, who chanted "Death to America" - the first time the chant has been heard in Tehran since the US attacks.
It has been suggested that the West is seeking Iran's assistance with - or at least agreement to - strikes against Afghanistan.
Iran condemned the attacks on the World Trade Center and the Pentagon. It is also hostile towards the ruling Taleban in neighbouring Afghanistan - where Osama Bin Laden, named by the United States as the prime suspect for the attacks, is sheltering.
But Iran is also one of the countries listed by the US as "a sponsor of terrorism" for its backing of Lebanon's Hezbollah militia and the Palestinian Hamas and Islamic Jihad militant groups.
Ayatollah Khamenei said Iran would not help any US-led coalition and it was audacity for the Americans to ask for assistance to attack a suffering Muslim country like Afghanistan.
Working together
The EU's External Relations Commissioner, Chris Patten, said the delegation wanted to find out how far Iran was prepared to work with Europe in fighting terrorism.
"The immediate target is Mr Bin Laden and (his) al-Qaeda group - those who appear to have been directly responsible for the atrocities in the United States - but beyond that the battle has to be carried forward in international fora and through international co-operation," he told reporters.
"I don't expect there will be a meeting of minds on all issues by a long way."
It was important for Iran to understand that the EU had clear views on human rights, he added, "and we have a very clear view that you can't distinguish between good terrorists and bad terrorists".
Economic ties
At the same time, Mr Patten said, the EU would hold out the prospect of a broader relationship with Iran, covering trade and investment, energy, drugs, asylum and refugees.
The prospect of enhanced economic and political ties with the EU as a reward for its support for international action against terrorism was held out to Pakistan - but only if the country moved towards restoring democracy.
Iran, fearing a new flood of Afghan refugees if the US launches strikes against Afghanistan, has welcomed a war on terrorism but says it must be carried out under the auspices of the United Nations.
Another EU delegation will travel to Washington on Thursday. Belgian Prime Minister Guy Verhofstadt and the President of the European Commission, Romano Prodi, will brief President George W Bush on decisions taken by EU leaders at an emergency summit in Brussels last Friday.