One of Iran's top nuclear negotiators signalled on Friday that talks with world powers could be extended beyond November's deadline, given big barriers standing in the way of a deal.

With both sides speaking of wide gaps in what limits should be placed on Iran's nuclear programme, the next round of talks will take place in Vienna on Tuesday and Wednesday.

But Iran's deputy foreign minister Abbas Araqchi, quoted by the Fars and ISNA news agencies, said there was already an acceptance that a November 24 deadline could be missed.

"Time passes quickly, we are not still disappointed but if we cannot get a good enough result from this round of talks, it is obvious that we will not reach an agreement by November 24," he said.

"Everything is possible even to extend the talks," he added, noting that Iran "expected some progress" during discussions on the issue in New York on the sidelines of the UN General Assembly last month.

Next week's Vienna round will centre on the two biggest areas of contention, Iran's enrichment of uranium and the lifting of US, European and UN sanctions imposed on Iran in recent years, Araqchi said.

"The two sides of the negotiations are serious," he added.

On Thursday, Iran said it had held "constructive" talks with a visiting delegation of the UN nuclear watchdog, regarding outstanding issues in Tehran's disputed atomic activities.

But Tero Varjoranta, deputy director general of the International Atomic Energy Agency, said the "technical meetings" on Tuesday and Wednesday did not resolve outstanding concerns on whether the Islamic republic's nuclear activities had military dimensions.

The IAEA disclosed in September that Iran had failed to meet an August 25 deadline to provide information on five points meant to allay fears it was developing nuclear weapons.

Iran insists its nuclear programme is entirely peaceful.

One of the IAEA's questions centres on Iran's purported experiments with large-scale high explosives.

Under an agreement reached in November 2013 with the IAEA, Iran has already responded to 16 of the 18 issues the agency identified as relevant to its nuclear activities.

After failing to reach an initial July deadline, Iran and the P5+1 group of nations -- China, the United States, France, Britain, Russia and Germany -- set November 24 as the date for a deal guaranteeing that Tehran's nuclear programme is used for exclusively peaceful means.