Iran's foreign minister was due to leave Saturday for a whirlwind diplomatic tour as world leaders scramble to salvage something from the wreckage of a key nuclear deal after Washington withdrew.
Mohammad Javad Zarif's tour starts two days after unprecedented Israeli strikes in Syria which a monitor said killed at least 11 Iranian fighters, triggering fears of a broader conflict between the two arch-enemies.
He will visit Beijing, Moscow and Brussels, a spokesman said, holding meetings with all of the remaining parties to the 2015 agreement.
Before leaving, Zarif published a government statement on his Twitter page, slamming the "extremist administration" of US President Donald Trump for abandoning "an accord recognised as a victory of diplomacy by the international community".
It reiterated that Iran was preparing to resume "industrial-scale" uranium enrichment "without any restrictions" unless Europe provided solid guarantees that it could maintain trade ties despite renewed US sanctions.
Zarif's delicate diplomatic mission was complicated by reports of clashes between Iranian and Israeli forces in Syria on Thursday.
The Syrian Observatory of Human Rights said Saturday that 11 Iranians were among the 27 pro-regime fighters killed in strikes by Israel, which has vowed to prevent Iran gaining a military foothold in neighbouring Syria.
Tehran, which has sought to avoid an escalation in regional conflict that could alienate its European partners, has not commented on whether its forces were hit.
Israel and its allies have blamed the Iranian Revolutionary Guards for initiating Thursday's exchange by launching missiles into the occupied Golan Heights.
The White House backed Israel's claims, accusing Iran of "reckless actions" that posed a "severe threat" to stability in the Middle East.
"Already this week, the IRGC (Revolutionary Guards) has fired rockets at Israeli citizens, and Iran's proxies in Yemen have launched a ballistic missile at Riyadh," it said.
Saudi Arabia is another of Iran's key regional rivals.
Trump spoke with British Prime Minister Theresa May on Friday, and "both leaders condemned the Iranian regime's provocative rocket attacks from Syria," the White House said.
Iran denies that version of events, saying the Israeli strikes were launched on "invented pretexts".
Protests in Iran
Demonstrators rallied in Tehran following Friday prayers to protest Trump's move.
"Officials shouldn't trust France and Britain. They will never abandon the US for us," said housewife Poormoslem.
A photo on the official Instagram site of supreme leader Ayatollah Ali Khamenei showed him reading a Farsi translation of Michael Wolff's scabrous account of the Trump White House, "The Fire and the Fury", quickly picking up more than 100,000 likes.
Analysts said Iran was determined to maintain the moral high ground in the coming weeks.
"For the first time, Iran has the chance to show the world they are not the rogue nation they are always presented as, that they negotiated in good faith and keep to their commitments," said Karim Emile Bitar of the Institute for International and Strategic Studies in Paris.
But the government of President Hassan Rouhani faces political challenges at home, where the economy was already suffering high unemployment and inflation before Trump's decision.
Many say sanctions allow the government to blame outsiders for its own bad decisions.
The Western trade diplomat gave the example of Iran's recent restrictions on transferring funds to the EU - an effort to control the rapid slide of the rial - that caused huge problems for importers.
"It's really annoying that the Iranian government is never blamed for the really bad decisions they have taken lately concerning business, and only the sanctions are blamed," she said.