TEHRAN (AFP) -- Iran on Monday urged the European parties to the 2015 nuclear deal "to take practical, effective and responsible decisions" to save the landmark agreement.

"We stress that the continued voluntary and goodwill based actions by the Islamic Republic of Iran are rooted in the principle of reciprocity of rights and duties" in the nuclear deal, the foreign ministry said in a statement.

On Sunday the European parties to the deal -- Britain, France and Germany -- called for dialogue as tensions further intensified between Iran and the United States.

In a statement, the so-called E3 expressed concern the deal was at risk of further unravelling but said it was up to Iran to ensure its survival.

The three European states were among the key players in the 2015 deal -- known as the Joint Comprehensive Plan of Action, or JCPOA -- on Iran's nuclear programme.

But US President Donald Trump in 2018 announced Washington was pulling out of the deal, to the dismay of its European allies.

Angered that its beleaguered economy is not receiving sanctions relief it believes it was promised under the deal, Iran has intensified its sensitive uranium enrichment work, prompting stern warnings from Washington.

In its statement on Monday, the foreign ministry in Tehran said the expectations of the Europeans were "unrealistic".

"Any expectation for Iran to return to the conditions prior to May 8, 2019 without proof of any political will and practical ability of the European parties" to ensure sanctions relief "is an unrealistic expectation".