European powers have said they remain committed to the Iran nuclear deal but that they "reject any ultimatums" from Tehran to prevent its collapse.
ran announced on Wednesday that it had suspended two commitments under the 2015 accord in response to the economic sanctions the US reimposed last year.
It also threatened to step up uranium enrichment if it was not shielded from the sanctions' effects within 60 days.
The EU, UK, France and Germany noted "with great concern" Iran's move.
The EU's foreign policy chief and the foreign ministers of France, Germany and the UK stressed that the JCPOA was "a key achievement of the global nuclear non-proliferation architecture, which is in the security interest of all".
"We strongly urge Iran to continue to implement its commitments under the JCPOA in full as it has done until now and to refrain from any escalatory steps," a joint statement said.
"We reject any ultimatums and we will assess Iran's compliance on the basis of Iran's performance regarding its nuclear-related commitments under the JCPOA and the NPT (Treaty on the Non-Proliferation of Nuclear Weapons)."