Ashton looks to closer EU ties on Iran visit

She said the nuclear negotiations, which are taking place in a separate format in Vienna, are “difficult, challenging” and “there is no guarantee [they] will succeed.”

But she noted that despite divisions between reformists and hardliners in the Iranian establishment: “One of the things that’s been very clear is the support that is given across the political spectrum [in Iran] for the work that is going on.”

Her host, Iranian foreign minister Mohammad Zarif, said he hopes a permanent nuclear accord can be reached “in four or five months."

Ashton added that if the nuclear talks go well, the EU is keen to deepen relations with the Islamic republic.

“Thinking about some of the issues in the region, for example the real challenges of the drug trade from Afghanistan. Iran faces real difficulties there. There are ways in which we could work together to try and address that. And then looking into the future, the possibilities of all sorts of dialogues and discussions; again an example would be the environment,” she said.

Following her meetings with civil society leaders, including women’s groups, she noted there is also potential to “move forward” on launching an EU-Iran “human rights dialogue.”

Her visit is the first time the EU sent its top envoy to Iran since her predecessor, Javier Solana, in 2008.

But it comes after a series of visits by EU countries’ foreign ministers and MEPs in recent months as relations warm up.

The Italian foreign minister went to Iran late last year, while the Polish and Swedish ministers went in February.

Poland’s Radek Sikorski last month noted that when he spoke out against censorship in his press conference, his remarks were censored in Iranian media.

NGOs also say that detentions of journalists and hangings have gone up since Iranian President Hassan Rohani, who depicts himself as a moderate, came to power last summer.

For its part, Israel said Ashton should not have gone in protest at Iranian arms shipments to EU-designated “terrorist” groups, such as Hamas in Gaza.

Israeli authorities last week intercepted a ship carrying rockets to Hamas, which they say came from Iran, although Iran denies, this.

"I would expect Catherine Ashton to cancel or at least postpone her visit to Tehran," Israeli intelligence minister Yuval Steinitz said.

"Nobody has the privilege to ignore the true, murderous actions of the regime in Tehran,” Israeli PM Benjamin Netanyahu added.