Iran nuclear deadline not a 'sacred date'

The end of June deadline for a nuclear deal between Iran and world powers is not sacred and extra time may be necessary, a top Iranian negotiator said on Tuesday.

Iran and the five permanent members of the UN Security Council plus Germany have set June 30 as the date for a comprehensive accord regarding Tehran's disputed nuclear programme.

But Abbas Araghchi, a deputy foreign minister and key member of the Iranian team, signalled that the final talks may overrun, having already said progress on drafting the deal has been very slow.

"The date... was selected for the end of negotiations but we will not sacrifice a good agreement for the sake of the schedule," he was quoted as saying on state television's website.

"If we need a few extra days it's not important because there are no sacred dates," he said of the talks with the United States, Britain, China, France, Russia and Germany.

With US officials also saying in the past week that the process of concluding the agreement is proving complicated, Iran's President Hassan Rouhani on Saturday criticised the powers for "haggling".

"If the other party respects the agreed framework and does not add other demands the differences can be resolved, but if they choose the path of haggling then it can prolong the negotiations," he said.

The two sides agreed the outlines for a deal on April 2 after intensive talks in the Swiss lakeside city of Lausanne went past a March 31 deadline.

The US has said June 30 remains its deadline and Rouhani noted that despite "many differences" during the negotiations he remains "hopeful" of an agreement.