Oil prices rose after OPEC's announcement, which analysts cited as evidence that investors believe the actual increase in production will be smaller, about 600,000 to 700,000 barrels a day.
OPEC sources also said Iran had demanded that USA sanctions be mentioned in the group's post-meeting communiqué.
Iran doesn't believe its customers will get waivers from the U.S. government that would allow them to continue crude purchases, Oil Minister Bijan Namdar Zanganeh said in a Bloomberg television interview yesterday.
After a meeting in Vienna, Emirati Energy Minister Suhail al-Mazrouei said the cartel chose to fully comply with its existing production ceiling. Furthermore, during the press conference following Friday's deal, the one question which never got an explicit answer is how much output would be boosted by, with little clarity shed beyond "targeting full compliance at the group level".
"Since as UAE's Energy and Industry Minister Suhail Mohamed Al Mazrouei, who is also the current chairman and president of OPEC, said at a press conference following the meeting, "[it] would not make sense if we allocated production to a country that can not produce it"!
Saudi Arabia's energy minister, Khalid al Falih, said the agreement would allow countries with spare production capacity to boost output.
The proposal is the result of a compromise hammered out in days of fractious talks in Vienna dominated by Iran's resistance to easing an 18-month-old supply-cut deal credited with lifting oil prices to multi-year highs. US President Donald Trump criticised Opec on Twitter for inflating the cost of fuel.
Now among OPEC members, Venezuela is the country whose production is well below the amount allowed under the 2016 agreement.
US crude jumped 2.9 percent Friday and Exxon Mobil advanced 2.1 percent.
Iran has objected to having members with additional capacity such as Saudi Arabia fill Venezuelan output gaps.
The agreement today will be reviewed at the extraordinary OPEC meeting in September.
State oil company Saudi Aramco had anticipated this week's decision and was already ramping up output, Al-Falih said.
Asked to what extent the decision to increase supply had been driven by pressure from Trump, Novak said: "It is obvious that we are not being driven by tweets but base our actions on deep market analysis".
"The real increase of production would be a figure exactly close to 1 million", Novak said in an interview with Bloomberg television.
Much of the shortfall has come from Venezuela, where an economic crisis has savaged petroleum production.
That Opec finally managed a consensus is a success in itself when seen in the perspective of the clear split within the group on the issue of increasing output. "I think at this stage 1 million barrels is reasonable".
"There was a lot of anticipation in the market that there was going to be a lot of new oil coming to market, and that isn't going to happen, at least for now", said John Kilduff, a partner at Again Capital.
US Energy Secretary Rick Perry will meet Russia's oil minister next week in Washington, a person familiar with the situation said on Friday, as the two countries compete to supply global markets with natural gas and crude.