This is the first time that Iran has issued an ultimatum since US President Donald Trump announced last week that Washington was withdrawing from the nuclear pact and reimposing crippling sanctions on Tehran, sparking worldwide concern and outrage.
The European Commission has been examining measures to counter the introduction of any US sanctions that might harm European businesses and is expected to unveil them to EU leaders at a summit in Sofia, Bulgaria, on Wednesday.
The U.S. decision to abandon the nuclear accord and recognize Jerusalem as the Israeli capital has made a combustible region - one with four ongoing conflicts - potentially all the more explosive, some analysts said.
Bolton was tapped by President Donald Trump in March to replace H.R. McMaster and is considered a hard-liner on many worldwide matters, including Iran.
"The agreement with Iran is working, we must do our utmost to preserve it", - Maja Kocijancic, spokeswoman for the head of European Union diplomacy Federica Mogherini.
Zarif's delicate diplomatic mission has been complicated by reports of clashes between Iranian and Israeli forces in Syria. It is the second leg of his tour during which he is to sit down with officials from 5 states in the JCPOA to discuss how Iran's interests under the deal can be guaranteed.
"The repeated attacks by the Zionist regime on Syrian territory were carried out under pretexts that were invented", he added.
Germany wants to help its companies continue doing business in Iran after the USA decision to reimpose sanctions against Tehran, but it could be hard to shield them from any fallout, Foreign Minister Heiko Maas said on Sunday.
Contrary to his woeful effort at explanation, this move will not make America safer.
Six regional powers, including the US, signed a nuclear agreement with Iran in July 2015, and economic sanctions on Iran were lifted in January the following year.
He said perhaps they feel that way in large part because representatives of the Obama administration were working in the past several weeks to try and prevent the deal from abrogating, which may have given the Europeans the false impression that they could prevail.
"Do we want to be vassals who obey decisions taken by the United States while clinging to the hem of their pants?"
White House national security adviser John Bolton says "regime change" in Iran is not now part of the administration's policy, despite his past suggestions that the United States should push for a new government in Tehran.
That is part of a flurry of diplomatic activity following Trump's unilateral withdrawal from what he called "a awful, one-sided deal", a move accompanied by the threat of penalties against any foreign firms doing business in Iran. Now, Iran will likely up the pressure on those US troops and on USA soldiers in Iraq.
This, along with its diplomatic moves to orchestrate an end to the Syrian conflict, has put Moscow at loggerheads with the U.S. and Europe, which have intervened against the regime.
"At this point, we have to replace the United States, which as an global actor has lost vigour, and because of it, in the long term, influence", he said.
"We do not see ourselves as a mediator between Iran and the U.S.", he said.