The departure of Tero Varjoranta comes at a sensitive time, three days after the United States announced it was quitting the 2015 nuclear deal with Iran.
European leaders have set to work on keeping the Iran nuclear deal alive, following Donald Trump's decision to pull out of the Joint Comprehensive Plan of Action or JCPOA. These would include: continued sale of Iran's oil and gas products; effective banking transactions with Iran; continued multimodal transport relations; new European Union investments in Iran; and a blocking mechanism to nullify U.S. sanctions on European Union firms.
Mogherini said she couldn't give any legal or economic guarantees to Iran about the continuation of the deal.
Mr Zarif told reporters as he left that the meetings had been "a good start", adding: "I believe we are on the right track, now a lot depends on what we can do within the next two weeks".
They also agreed to "initiate work to protect European companies negatively affected by the U.S. decision", which involves Washington reimposing sanctions on Iran. Analysts say Kerry is blurring the line between legitimate advocacy and illegitimate efforts to sabotage the actions of a sitting USA government.More news: UK to produce 'significant' white paper on Brexit plans
Tehran is being given assurances that European governments will seek to protect companies doing business in Iran from renewed US sanctions, as foreign ministers prepare to meet in Brussels to salvage the nuclear deal.
Iranian officials have threatened to resume enrichment.
"Trump played his first card, but miscalculated the second move... as Iran did not follow that plan", Rouhani said according to the Iranian agency.
Mogherini acknowledged the enormous challenge of finding a way around USA sanctions punishing businesses trading with Iran. Iran has since been in talks with the other signatories to ensure the deal continues.
But European diplomats briefed on the Brussels meeting acknowledged that the EU support, however honest, risked looking hollow after Trump last week reimposed an array of wide sanctions on the Islamic Republic that will hit European companies investing in Iran.More news: Yanny vs Laurel: the debate rages on
He admitted though that United States sanction would "serve as a deterrent to businesses".
The crisis, potentially plunging the USA and Europe into a sanctions war and raising serious questions about European economic sovereignty, will also be discussed at a meeting of EU heads of state on Wednesday in Sofia.
Speaking after her meeting with Zarif, Mogherini said the European Union had agreed to start work on a multi-level stream of work created to keep the Iran deal alive.
According to France 24 news agency, some European countries have been working out measures to bypass United States anti-Iranian sanctions since January 2018. Johnson said regime change in Iran was not a policy Britain should pursue.
"The EU will continue fighting for a rules-based worldwide system despite recent decisions on climate change, tariffs and Iran", the source said after the leaders met over dinner in Sofia.More news: Fortnite Duck Locations - Where To Find Rubber Duckies!
All sides were aware that urgent solutions are needed, the EU's top diplomat added, "not for the sake of a calendar but because if you want to save this deal.we know that the sooner we manage to do it, the better". "But we need to be sure that we have done everything in our power, and within the limits of the global trade rules, to avoid a negative scenario", Tusk said.