Friday's meeting, set to take place in Istanbul, will be the first since Israel's mid-June attack targeting key nuclear and military sites in the Islamic republic sparked a 12-day war.

The United States joined its ally Israel in the offensive, striking three Iranian nuclear facilities overnight between June 21 and 22.

"Especially after the recent war, it is important for them to understand that the Islamic Republic of Iran's position remains unshakable, and that our uranium enrichment will continue," said Foreign Minister Abbas Araghchi.

"We will not give up this right of the Iranian people," he said, quoted by Tasnim news agency.

The hostilities between Iran and Israel broke out just two days before Tehran and Washington were set to resume negotiations on Iran's nuclear programme.

Britain, France and Germany -- alongside China, Russia and the United States -- are parties to a 2015 nuclear deal with Iran, which placed major restrictions on its atomic activities in return for the gradual lifting of UN sanctions.

However, in 2018, the United States unilaterally withdrew from the agreement during Donald Trump's first term as president and reimposed its own sanctions.

Britain, France and Germany maintained their support for the 2015 accord and sought to continue trade with Iran, meaning UN and EU sanctions were not reinstated.

But they have since accused Tehran of failing to uphold its commitments and are threatening to reimpose sanctions under a clause in the agreement that expires in October -- something Iran is keen to avoid at all costs.

"Inaction by the E3 is not an option," a European source said of the three powers, noting that Tehran would be reminded during the meeting that the snapback window closes this autumn.

The source said Europeans were preparing to trigger the mechanism "in the absence of a negotiated solution" and called on Iran to make "clear gestures" regarding uranium enrichment and the resumption of cooperation with the UN's nuclear watchdog, the International Atomic Energy Agency.

The IAEA says Iran is the only non-nuclear-armed country currently enriching uranium to 60 percent -- far beyond the 3.67 percent cap set by the 2015 accord.

That is a short step from the 90 percent enrichment required for a nuclear weapon.

Western powers, led by the United States and backed by Israel, have long accused Tehran of secretly seeking nuclear weapons.

Iran has repeatedly denied this, insisting its nuclear programme is solely for civilian purposes such as energy production.

Tehran and Washington had held five rounds of nuclear talks starting in April, but a planned meeting on June 15 was cancelled after Israel launched its strikes on Iran.