French accusations that Iran was behind a foiled bomb plot near Paris could not have come at a worse time for its moderate president and his hopes of EU support against crippling new US sanctions.
Tuesday's allegations are a blow to President Hassan Rouhani, and hit just as European governments are working on a mechanism to allow Iran to continue to reap the economic benefits of compliance with a landmark 2015 nuclear deal abandoned by US President Donald Trump in May.
"Such allegations, whether true or not, at this moment of time will serve only to harm both Rouhani's government and the Iranian nation, and political moderation in Iran in general," said Saeed Leylaz, a lecturer at Tehran's Shahid Beheshti University.
The European parties to the nuclear agreement - Britain, France and Germany - have made no secret of their anger at the unilateral move by Trump and his administration to withdraw and seek to enforce renewed US sanctions internationally.
Iran was quick to deny the French allegations that Tehran was behind the attempted bombing of a June 30 rally held by an exiled opposition group, the People's Mujahedeen of Iran (MEK), dubbed "terrorists" by Tehran.
Iran "completely and forcefully" rejects the accusations, foreign ministry spokesman Bahram Ghasemi told AFP.
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But the allegations echo the Trump administration's charges against Tehran - that it is a state sponsor of "terrorism" abroad - and the French government's response - asset freezes on the intelligence ministry and two of its alleged operatives - mirror those taken by the US administration.
"Any tension between Iran and Europe - especially France - is in line with the wishes of radicals in Tehran and Washington and Tel Aviv and Riyadh," said Leylaz, who is seen as close to Iran's reformists.
"I am certain this (the allegation) is a source of worry for the government, because it happened while the Islamic republic needs every single relation and link with the West minus the United States," he added.
Rouhani, who was re-elected to a second four-year term last year on the promise of greater economic dividends from his government's opening to Washington, was already reeling from the economic fallout of Trump's abandonment of the nuclear deal.
A precipitous slide in the value of the rial against the dollar hit the purchasing power of ordinary Iranians, while an anticipated boost to Western investment failed to materialise, hitting plans to renew Iran's antiquated infrastructure.
Rouhani had counted on EU governments to work with the other parties to the deal - China and Russia - to mitigate the impact of the US policy U-turn but the French allegation has now put those hopes in jeopardy.
The allegations were swiftly seized on by the Trump administration as vindication of its hard line.
"France taking strong action against failed Iranian terrorist plot in Paris -- Tehran needs to know this outrageous behaviour will not be tolerated," the White House's National Security Council tweeted.
Rouhani's government sees the hand of the Trump administration behind the allegations, convinced Washington is determined to undermine European resistance to the US abandonment of the JCPOA, the official acronym for the nuclear deal.
"Some centres of power do not approve of Iran's good relations with Europe - that it is staying in the JCPOA and that its economic ties with the EU continue," Ghasemi said.
Prominent conservative analyst Amir Mohebbian voiced scepticism about the French allegations, saying it made no sense for Iran to get involved in an operation that so clearly endangered its own interests.
"There is no logical reason for the Islamic republic to take such actions in the present sensitive situation," Mohebbian said.
"Iran is acting transparently. It has created transparent and close diplomatic relations with Europe.
"Iran does not want to do something that will damage these good relations." Mohebbian said the allegations were deliberately timed to cause maximum damage to Iran's foreign policy interests.
"The possibility of an intelligence trap for damaging Iran's relations with the European Union... is not far-fetched," he said.
"I am not aware of the legal aspects of the allegations, but it is clear that the beneficiary of these events is the MEK," he said.
Senior members of Rouhani's government have gone further, accusing the MEK itself of being behind the alleged plot.
Foreign Minister Mohammad Javad Zarif said it was a "false flag ploy" by the MEK, which has been outlawed in Iran since 1981 and was on the European Union's terrorism blacklist until 2009.