By Agence France-Presse
"France taking strong action against failed Iranian terrorist plot in Paris -- Tehran needs to know this outrageous behavior will not be tolerated," the White House's National Security Council tweeted.
State Department spokeswoman Heather Nauert told reporters the incident reinforced that Iran was "the world's top sponsor of terrorism."
France said Tuesday it was freezing assets of two suspected Iranian intelligence operatives over an alleged plot to bomb a rally in Paris three months ago.
The event was being held by the armed opposition group the People's Mujahedin of Iran (MEK), which Tehran considers a terrorist group but which Western powers have removed from its blacklists.
Iran immediately denied any involvement, as it did in July when the MEK accused it of being responsible.
The incident comes after President Donald Trump pulled out of an international agreement on curbing Iran's nuclear program, defying allies including France which says that the deal is working.
The Trump administration has vowed to curtail Iranian influence and criticized the Europeans for seeking to evade impending US sanctions on transactions with Iran.
European officials, and the administration of former president Barack Obama, pointed to divisions in Iran's government and hoped to strengthen moderates such as President Hassan Rouhani over elements in the security and clerical establishments that are deeply hostile to the West.
The US considers Iran to be the world's biggest state sponsor of terrorism because of its links with a host of armed groups, particularly the powerful Hezbollah militia in Lebanon and Hamas in the Palestinian territories, as well as other networks in Iraq and Yemen.