"Qatar has chose to withdraw its membership form Opec effective January 2019 and this decision was communicated to Opec this morning", he told a news conference, adding that Qatar would still attend an Opec meeting in Vienna this week.
Qatar will withdraw from Opec on January 1, Qatari Energy Minister Saad Sherida Al Kaabi announced on Monday.
Kaabi said OPEC had been informed of the decision on Monday ahead of the announcement and that he would still attend the organisation's Vienna meeting later this week, his "first and last" as energy minister.
He added, "Qatar has worked diligently during the past few years to develop a future strategy based on growth and expansion, both in its activities at home and overseas".
Naeem Aslam, an analyst at online broker ThinkMarkets, said: "Qatar leaving Opec isn't great news for the oil market and the market participants haven't digested the full impact of this news".
"The nature of the animal as far as Opec is concerned is the bigger production capacity you have then the more weight you carry", Vandana Hari, founder and chief executive of Vanda Insights, told The National.
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According to the energy minister, the decision is not connected to the political and economic boycott of Qatar pushed by its powerful neighbor Saudi Arabia since June 2017 and supported by three other Arab nations. "They are not a big producer, but have played a big part in it's (Opec) history", the source said.
That meeting is expected to set a policy for 2019 and despite Qatar's announcement, oil prices soared on Monday after Russian Federation and Saudi Arabia renewed a pact to cap output.
Doha said it wants to increase LNG production from 77 to 110 million tonnes annually.
Qatar has been an OPEC member for 57 years.
Oil prices surged about 5 per cent on Monday after the United States and China agreed to a 90-day truce in their trade war, but Brent crude is still trading at around $62 a barrel, well below October's peak of more than $86.