U.S. West Texas Intermediate (WTI) crude futures CLc1 settled unchanged at $71.49, after earlier also hitting their highest since November 2014 at $72.30 a barrel.
Asia's demand is at record highs and with rising prices its crude could cost $1 trillion this year, about twice what it paid during the market lull of 2015/2016.
Brent crude oil reached an intraday peak of $79.47 a barrel, up $1.24 and its highest since November 2014, before retreating to $78.14, down 9 cents by 10:09 EDT.
Members of the Organization of Petroleum Exporting Countries, including Saudi Arabia, Kuwait and the United Arab Emirates, said they have enough capacity to fill in any supply gap if renewed sanctions curtail Iran's exports.
Late last week, US National Security Advisor John Bolton made it clear that Washington may slap sanctions on European Union companies cooperating with Tehran after the US administration's withdrawal from the Iran nuclear deal, also known as the Joint Comprehensive Plan of Action (JCPOA).
Crude has rallied this month after U.S. President Donald Trump pulled out of a nuclear agreement with world powers that had eased sanctions on Iran in exchange for curbs on its atomic program.
A worker walks at the Zubair oilfield in Basra, Iraq May 9, 2018.
Over the last three years, the two countries have been a seesaw of production.
Opec and other producers such as Russian Federation have restrained supplies in support of higher prices.
India, the third-largest consumer of oil after the USA and China, would be especially hard-hit if prices keep rising.
Oil rose to $80 a barrel in London for the first time since 2014 as US crude inventories fell and traders braced for the impact of renewed sanctions on OPEC member Iran.
The two ministers, in a joint statement, blamed volatility in prices on worldwide political tensions.
"The recent jump in oil prices will take its toll", said the agency.
"With trade skirmishes between the United States and China and all kinds of political issues, I see resistance from Chinese crude buyers to comply" with U.S. sanctions, said Victor Shum, vice president of the Energy group at IHS Markit, on CNBC TV.
Oil and gas research analyst Jack Allardyce at cantor Fitzgerald Europe said: "There is now a firmer consensus around the potential impact of lost Venezuelan/Iranian exports, and as such, we see little to drive benchmarks much higher in the immediate term".
Further supporting prices, Royal Dutch Shell (RDSa.L) said it was halting crude exports from a major Nigerian pipeline.
The Paris-based IEA cut its forecast for global demand growth to 1.4 million barrels per day for 2018, from a previous estimate of 1.5 million bpd.
"The current market deficit points to a further decline in stocks", Commerzbank said in a daily note.
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