Iran does not expect to raise its oil exports immediately after Sunday's nuclear deal, but is in talks with potential western investors in its energy industry, Iranian oil minister Bijan Zanganeh told the Financial Times newspaper.

Iran and six world powers reached a deal on Sunday to curb Tehran's nuclear programme in exchange for limited sanctions relief.

A senior Iranian industry official had said on Tuesday that the deal should make it easier to export Iran's oil, thanks largely to plans to ease a European shipping insurance ban.

But Zangeneh told the FT in an interview he did not expect any immediate impact on Iran's crude oil exports.

European Union (EU) officials said on Monday that some sanctions on Iran might be relaxed in December, but it could be January before the necessary legislative changes are made.

US and EU sanctions that have slashed Tehran's oil exports from 2.5 million barrels per day (bpd) to around 1 million remain in place and Washington has said it will not allow exports to rise for at least six months.

Iran is home to some of the world's largest oil and gas reserves, but US energy firms have been barred by Washington from Iran for nearly two decades.

Many of Europe's biggest oil and gas companies had planned multi-billion dollar investments to help develop Iranian reserves. But US pressure drove them away from Iran in the late 2000s for fear of jeopardising their US interests.

Strict Western bans on any investments in Iran's energy sector remain firmly in place.

But Zangeneh told the FT he had already met with European companies and "indirectly" with US groups to prepare for the day when they might be allowed back in by their governments.

Meanwhile, Iran will press on with construction at a nuclear reactor site at Arak, Iranian Foreign Minister Mohammed Javad Zarif said.

The uncompleted heavy-water research reactor emerged as one of several crucial issues in negotiations in Geneva last week, when Iran agreed with six world powers to curb Tehran's nuclear programme for six months in return for limited sanctions relief.

Iran said it would not make "any further advances of its activities" on the Arak reactor, according to text of the agreement.

"The capacity at the Arak site is not going to increase. It means no new nuclear fuel will be produced and no new installations will be installed, but construction will continue there," Zarif told parliament in translated comments broadcast on Iran's Press TV.

But experts have said an apparent gap in the text could allow Tehran to build components off-site to install later in the nuclear reactor. It was not immediately clear if Zarif was referring to this or other construction activity.

Tehran has said it could open the reactor as soon as next year. It says its purpose is only to make medical isotopes, but Western countries say it could also produce plutonium, one of two materials, along with enriched uranium, that can be used to make the fissile core of a nuclear bomb.  - Reuters