"We are entering a new phase with this 30 days that is now giving us also the opportunity to really find diplomatic ways to find a solution," Kallas told journalists.

"We have this 30 days to sort things out," she added.

France, Britain and Germany on Thursday set off a mechanism that could reimpose United Nations sanctions on Iran in 30 days for failing to comply with commitments over its nuclear programme it agreed to a decade ago.

That came after weeks of warnings over Iran's alleged breaches of the 2015 agreement with world powers to curb its nuclear programme. The sanctions were suspended under the deal.

Iran warned that it would "respond appropriately" to the step, which risks ending the most sustained diplomatic push in years for a peaceful solution to the Iranian nuclear crisis.

But the United Nations has also said the next 30 days represents a "window of opportunity" to strike a new deal.

France's foreign minister Jean-Noel Barrot said that "Iran's nuclear escalation must not go any further" but emphasised the move "does not signal the end of diplomacy".