"It is surprising and regrettable that, in a situation where diplomatic interactions and exchanges of messages are continuing... to finalise the negotiations," the three European parties would issue such an "unconstructive" statement, Iran's foreign ministry spokesman Nasser Kanani said.

The remarks came after the trio raised "serious doubts" about Iran's sincerity in seeking a revived nuclear agreement and warned that the Islamic republic's position was jeopardising the prospects of reaching a deal.

"The three European countries are advised to play a more active role to provide a solution to end the few remaining disagreements instead of entering the phase of destroying the diplomatic process," Kanani said.

The three European parties to the deal said Saturday that Tehran "has chosen not to seize this critical diplomatic opportunity", adding that "instead, Iran continues to escalate its nuclear programme way beyond any plausible civilian justification".

Tehran has also reopened issues related to its legally binding obligations under the Non Proliferation Treaty that was concluded with the UN atomic energy watchdog IAEA, they added.

Kanani said it was "regrettable that the three European countries have taken a step in the path of the Zionist regime to defeat the negotiations with this ill-considered statement," referring to Israel, the Islamic republic's arch-foe and a staunch opponent of the deal.

"If such an approach continues, they must also accept responsibility for its results," he said.

The 2015 agreement, known formally as the Joint Comprehensive Plan of Action or JCPOA, gave Iran sanctions relief in return for restricting its nuclear program.

But in 2018, then president Donald Trump withdrew the US from the deal and began reimposing biting sanctions, prompting Tehran to roll back on its commitments under the agreement.

The negotiations in Vienna since April 2021 have aimed to restore the deal by lifting the sanctions on Tehran once again and pushing Iran to fully honour its obligations.

Last month, the European Union, which acts as the mediator of the talks, put forward a "final" draft of the agreement.

Iran and the US then took turns to respond to the text, with Washington saying on Friday that Iran's latest reply was a step "backwards".

Kanani said Saturday that "threats and sanctions" would not "prevent the Iranian people from pursuing their rights and securing their interests."