Iran "is ready to forge a realistic and lasting bargain that entails ironclad oversight and curbs on enrichment in exchange for the termination of sanctions", wrote Foreign Minister Abbas Araghchi.

"Failing to seize on this fleeting window of opportunity may have consequences destructive for the region and beyond on a whole new level."

The message was addressed to the so-called E3 group of nations -- France, Germany and the UK -- involved talks with Iran over its nuclear programme.

At the end of August, the E3 nations triggered a mechanism to reimpose UN sanctions on Iran for failing to comply with commitments over its nuclear programme signed a decade ago.

Under the "snapback" mechanism, they gave Iran a month to negotiate before sanctions were reimposed.

EU foreign policy chief Kaja Kallas met Araghchi on Thursday to seek a "negotiated solution" to the standoff.

The 2015 deal negotiated under former US president Barack Obama offered Iran sanctions relief in return for drastically scaling back its nuclear work.

But President Donald Trump withdrew from the deal during his first term and imposed sweeping sanctions, including on countries that bought Iranian oil.

Western countries accuse Iran of seeking to acquire nuclear weapons -- something Tehran denies, defending its right to what it insists is a civilian nuclear program.