British Foreign Secretary Philip Hammond
British Foreign Secretary Philip HammondReuters

Iran will need to show more flexibility to reach a nuclear deal with six world powers, British Foreign Secretary Philip Hammond said on Monday, according to the International Business Times.

Speaking to reporters in Luxembourg, Hammond also suggested the talks might go on beyond a 30 June deadline.

"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," he said.

"So I think the serious negotiations are now getting under way and over the next week or so I hope we will start to see some real progress," added Hammond, who is expected to hold talks 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 30 June deadline slipped by a few days, he said, "Let's see where we get to. We are pushing hard to get there."

Iran and the six powers reached a framework agreement in April but are in disagreement over many remaining issues as they try to reach a final deal by the June 30 deadline.

In fact, two diplomats said last week that the sides are still apart on all main elements of the nuclear deal, describing the draft of a main document as a patchwork of text and dozens of blank spaces because of stubborn disagreement on up to 10 crucial points.

The comments are in line with ones made by a diplomat who had spoken with a Russian news agency and said the talks are “virtually stalled”.

Speaking after the latest round of discussions in Vienna, the diplomat said talks had made no significant progress and added, “The process has virtually stalled, there is a risk that the deadline will have to be postponed again.”

Russia later expressed concern over the "very worrying" slowdown in progress in the nuclear talks.

"The rate of progress... is progressively slowing down," Russia’s chief negotiator, Sergei Ryabkov, said. "This is very worrying to us because there is very little time before the deadline and we urgently need to enter the final stage.”

Among the unresolved issues are the pace of easing Western sanctions imposed over the Iranian program and the monitoring and verification measures to ensure Iran could not pursue a clandestine nuclear weapons program.

Iran has categorically deniedreports that it would allow inspectors into its sites as part of a final deal, describing them as mere rumors and as wrong interpretations of the understanding reached in early April.

Iran’s Deputy Chief of Staff recently reiteratedthat the Islamic Republic will not allow any inspection of its military sites, calling the demand to do so “excessive”.