“There will need to be some more flexibility shown by our Iranian partners if we are going to reach a deal, but, look, this is a negotiation, we always expected it would go right to the line and maybe beyond the line,” Hammond told reporters as he arrived for a European Union foreign ministers meeting in Luxembourg.

“So I think the serious negotiations are now getting underway and over the next week or so I hope we will start to see some real progress,” he said.

Hammond is due to hold talks later with Iranian Foreign Minister Mohammad Javad Zarif as well as the EU’s foreign policy chief Federica Mogherini and the foreign ministers of Germany and France.

Asked if it would matter if the June 30 deadline slipped by a few days, he said: “Let’s see where we get to. We are pushing hard to get there.”