The E3 letter follows months of diplomatic stalemate, particularly after a 12-day war between Iran and Israel in June.

The top diplomats of Britain, France, and Germany threatened to reimpose sanctions on Iran as an end-of-the-month deadline nears for the country to resume negotiations with the West over its nuclear program and cooperation with the United Nations nuclear watchdog.

Britain, Germany and France have told UN officials that snapback sanctions are on the table if Iran does not sit down to negotiate over its nuclear weaponry.