By John Irish and Guy Faulconbridge
PARIS/LONDON (Reuters) - France, Britain and Germany formally triggered the dispute mechanism in Iran's nuclear deal on Tuesday, the strongest step the Europeans have taken so far to enforce an agreement that requires Iran to curb its nuclear programme.
The European powers said they were acting to avoid a crisis over nuclear proliferation adding to an escalating confrontation in the Middle East. Russia, another signatory to the pact, said it saw no grounds to trigger the mechanism and Iran dismissed the step as a "strategic mistake".
The three European countries said they still wanted the 2015 nuclear deal to succeed and were not joining a "maximum pressure" campaign by the United States, which abandoned the pact in 2018 and has reimposed economic sanctions on Iran.
Triggering the mechanism amounts to formally accusing Iran of violating the terms of the deal and could lead eventually to reimposing U.N. sanctions that were lifted under the pact.
Iran's foreign minister criticised the move.
"The usage of the dispute mechanism is legally baseless and a strategic mistake from a political standpoint," Minister Mohammad Javad Zarif said, according to the Fars news agency.
Iran has gradually rolled back its commitments under the accord since the United States quit. Tehran argues that it has the right to do so because of Washington's actions.
"We do not accept the argument that Iran is entitled to reduce compliance with the JCPoA," the three European countries said in a joint statement, using the formal name of the agreement, the Joint Comprehensive Plan of Action.
"Our three countries are not joining a campaign to implement maximum pressure against Iran. Our hope is to bring Iran back into full compliance with its commitments under the JCPoA," they said.
Iran has long accused the Europeans of reneging on promises to protect its economy from U.S. sanctions. Foreign Ministry spokesman Abbas Mousavi dismissed the "completely passive action" of the three countries.
He said Iran would support any act of "goodwill and constructive effort" to save the agreement but would give a "serious response to any destructive measures."
Russia's Foreign Ministry said activating the mechanism could make it impossible to resume implementation of the deal.
CONFRONTATION
To trigger the mechanism, the European states notified the European Union, which acts as guarantor of the agreement. EU foreign policy chief Joseph Borrell said the aim was not to reimpose sanctions but to ensure compliance.
After months of gradual steps to reduce compliance, Iran said on Jan. 6 it would scrap limits on enriching uranium.
The nuclear diplomacy is at the heart of a broader confrontation between Iran and the United States, in which Washington killed an Iranian general in a drone strike in Baghdad and Tehran responded by launching missiles on U.S. targets in Iraq.
"Given recent events, it is all the more important that we do not add a nuclear proliferation crisis to the current escalation threatening the whole region," the European states said, adding that their aim was preserving the deal.
U.S. President Donald Trump abandoned the nuclear deal reached under his predecessor Barack Obama, arguing it was too weak and new sanctions would force Iran to accept more stringent terms. Iran says it will not negotiate with sanctions in place.
British Prime Minister Boris Johnson said on Tuesday: "If we're going to get rid of it, let's replace it and let's replace it with the Trump deal."
The U.S. Special Representative for Iran, Brian Hook, said Washington was "very pleased" by Johnson's comments. He also said the United States would like France, Britain and Germany to join its efforts of diplomatic isolation against Tehran.
Under the mechanism, the EU should inform the other parties - Russia and China as well as Iran - of the move. There would then be 15 days to resolve differences, a deadline that can be extended or ultimately lead to reimposing U.N. sanctions.
In Jerusalem, Israeli Prime Minister Benjamin Netanyahu said Israel woud not allow its arch-foe Iran to obtain nuclear weapons and called on Western countries to impose "snapback sanctions" on Tehran under the previous U.N. resolutions.
"We know exactly what is happening with the Iranian nuclear program. Iran thinks it can achieve nuclear weapons. I reiterate: Israel will not allow Iran to achieve nuclear weapons," Netanyahu said.