Iran has taken strong exception to the statement by three European signatories to the nuclear deal, calling it "ill-considered" and "against the goodwill" to salvage the deal.

In a statement on Saturday, Iran's Foreign Ministry spokesperson Nasser Kanaani accused the E3 countries –– France, Britain, and Germany –– of toeing the Israeli line and warned that they would be held responsible if the talks to revive the 2015 nuclear deal fail.

Kanaani 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.

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

The remarks came in response to a joint statement by France, Britain, and Germany on Saturday that hit out at Tehran for its demand to close the UN nuclear watchdog's investigation into three undeclared nuclear sites, blaming Iran for "jeopardising" the talks.

'Destroying the diplomatic process'

Last week, Iran submitted its latest response to US comments on the European Union draft proposal aimed at reviving the 2015 accord, describing it as "constructive."

The three European countries, however, said Iran's response marks a step backward, as it ties the revival of the landmark deal, known officially as the Joint Comprehensive Plan of Action (JCPOA), to the International Atomic Energy Agency (IAEA) probe.

"This latest demand raises serious doubts as to Iran's intentions and commitment to a successful outcome on the JCPOA," read the joint statement, adding that Iran's position "contradicts its legally binding obligations and jeopardises prospects of restoring the JCPOA."

Kanaani dismissed the E3's reservations, terming the statement "surprising" and "regrettable" at a time when the talks to revive the agreement, underway since April last year, are in the final stretch.

He termed the resolution against Iran at the IAEA board of governors meeting in June as an "inappropriate and political action," urging the E3 countries to "not enter the phase of destroying the diplomatic process" and to "provide a solution to end the few remaining disagreements" between Iran and the US.

The IAEA's board of governors is meeting again on Monday, almost three months after passing the anti-Iran resolution over Tehran's non-cooperation with the agency.

On Wednesday, the UN nuclear watchdog said Iran's stock of uranium enriched up to 60 percent purity was close to weapons grade with many questions still unanswered.

“Given Iran’s failure to conclude the deal on the table, we will consult, alongside international partners, on how best to address Iran’s continued nuclear escalation and lack of cooperation with the IAEA regarding its NPT (non-proliferation treaty) safeguards agreement,” the E3 said in its statement on Saturday.

The negotiations between Iran and the P4 1 countries (Russia, China, the UK, France, and Germany) to revive the 2015 deal the US withdrew from in 2018 have been hampered by the standoff between Tehran and the UN nuclear watchdog, especially since June.

According to observers, Iran's insistence on dropping the probe into three undeclared sites and the IAEA's refusal to accept the demand has put a major roadblock in the revival of the deal and de-escalation of tensions.

The 2015 agreement 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.