Mohammad Javad Zarif held talks lasting more than an hour with Baroness Ashton, who is making her first visit to Tehran amid a thaw in relations.

"We can do it in four or five months and even shorter," Mr Zarif said.

Baroness Ashton cautioned there was "no guarantee" her talks would lead to a comprehensive agreement.

World powers want Iran to scale back its nuclear work to ensure it cannot assemble a nuclear weapon.

The election of Iranian moderate Hassan Rouhani as president last year led to an improvement in ties between the Islamic Republic and the EU.

In November, Baroness Ashton helped broker a deal to curb Iran's nuclear programme in return for limited sanctions relief.

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Mrs Ashton has been widely credited with playing a key role in negotiating the landmark interim deal between Iran and world powers last November”

Lyse DoucetChief international correspondent, Tehran

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Analysts say the war in Syria is also expected to be discussed, as Iran is a key ally of President Bashar al-Assad.

It is the first visit to Iran by an EU policy chief since 2008.

"This interim agreement is really important but not as important as a comprehensive agreement [which is]... difficult, challenging," Baroness Ashton said at a joint news conference with Mr Zarif.

"There is no guarantee that we will succeed."

There was, she added, a need for support from all sides.

Mr Zarif said Iran had shown good faith and political will, adding: "We have done our side. It is up to the other side... to come to the negotiating table with a desire, decision and commitment to reach a mutually acceptable agreement."

Baroness Ashton also held talks with President Rouhani and Parliament Speaker Ali Larijani in separate meetings on Sunday.

Baroness Ashton held talks with President Rouhani at a separate meeting

The BBC's Lyse Doucet, who is in Tehran, says the visit is primarily aimed at exploring the potential for a new relationship between Iran and Europe.

But it is hoped Baroness Ashton can send a message to Iran's leaders that there is much to gain if they continue to build a new relationship with the international community, she adds.

Last year's interim deal with the so-called P5+1 - the US, UK, France, China and Russia plus Germany - saw Iran curb uranium enrichment.

The next high-level talks are scheduled for Vienna on 17 March.

Iranian media say the trip will also take Baroness Ashton to the historical city of Isfahan on Monday.