Zanganeh's forecast, delivered before a looming June 30 deadline to finalise Iran's historic nuclear power deal with world powers, was revealed at a two-day OPEC seminar in Vienna ahead of the cartel's output meeting on Friday.
Questioned about the Islamic republic's oil output, he told delegates: "We believe that immediately, or after one month of lifting the sanctions, (we will achieve) half a million (extra) barrels per day, and after 6-7 months we will achieve one million barrels."
"Iran, because of the sanctions and limitations, has reduced production and exports."
Iran currently exports 1.3 million bpd, against 2.2 million bpd before the sanctions were imposed about one decade ago.
"It's fair we return to the level of the production (which Iran had) before the sanctions," Zanganeh added.
"OPEC members countries will consider the return of Iran to the market, and it will not have a negative impact on the market," he said amid ongoing concern about global oversupply which sparked the recent oil price slump.
In April, Iran and six world powers agreed the outlines of a historic deal that -- if it can be finalised by the target of June 30 -- would see painful US and EU sanctions strangling Iran's oil exports lifted.
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Sanctions would not be eased immediately, however; they would only be lifted once the UN atomic watchdog has verified that Tehran has dramatically downsized its nuclear programme.
US Secretary of State John Kerry said in April that he expected this to take between six months and a year.
The accord is aimed at making it virtually impossible for Iran to develop nuclear weapons.
Later this week, meanwhile, the 12-nation Organization of the Petroleum Exporting Countries (OPEC) is expected to hold its official daily output ceiling at 30 million barrels per day.
The cartel is expected to refrain from altering production despite a glut that has sent prices slumping 60 percent between June and January.
World oil prices were also hit by OPEC's decision in November to hold output in a bid to hurt US shale producers and preserve market share.
Prices slumped to six-year lows in January, but have since recovered to trade at about $60. However, they remain around 50 percent lower than at the same stage last year.
Zanganeh said Wednesday that the cartel needs to find a "fair price" for its oil.
"OPEC needs an equitable price -- a price that would not be harmful to global economic growth and allow investments to continue... and allow for the development of production capacity in member countries thus allowing continuity and stability," he said.