By Alex Lawler, Ahmad Ghaddar and Lewis Jackson
LONDON, Aug 27 (Reuters) - Six months into the Iran war, the world's most powerful oil alliance, OPEC+, finds itself in an unfamiliar position: unable to influence a market it once helped shape.
The war, which has shut a major export route for Middle Eastern oil and damaged energy infrastructure in several OPEC countries, has eroded the group's market share and, with it, its ability to affect prices. Its statements and policy decisions barely move oil markets
anymore.
Instead, cuts in Chinese crude imports have emerged as one of the dominant themes of 2026, helping to balance oil markets amid what analysts describe as the worst-ever supply disruption.
OPEC+ — the Organization of the Petroleum Exporting Countries and allies including Russia — accounted for about 40% of global oil output in July, according to Reuters calculations based on International Energy Agency data.
That's down from more than 48% before the U.S. and Israel attacked Iran in late February, although about four to five percentage points of the decline were due to the United Arab Emirates' withdrawal from OPEC in May.
OPEC+'s core group of seven producers, including Saudi Arabia and Russia, accounted for only a quarter of world oil output in July.
The war has reduced OPEC+'s ability to quickly raise or cut supply by effectively shutting the Strait of Hormuz, a key export route for top OPEC producer Saudi Arabia and other members such as Iraq and Kuwait.
OPEC was formed in 1960, and the expanded OPEC+ framework was created in 2016 when Russia and other producers joined efforts to help the group counter its shrinking share of world oil production.
OPEC's share of global crude output peaked at about 50% during the oil crises of the 1970s before falling to 30% by the mid-1980s as output from the North Sea, Alaska and Siberia increased.
OPEC did not reply to a Reuters request for comment. OPEC+ says its decisions are aimed at supporting market stability and it does not target a specific oil price.
Wartime supply disruptions are not new for OPEC, from Kuwait during the 1990-91 Gulf War to Iraq following the 2003 U.S.-led invasion. What is unusual now is the scale of the outage, which is constraining multiple producers simultaneously, reducing the group's ability to offset losses elsewhere.
Since March, the core OPEC+ group has announced six oil output increases. Yet, because of the Hormuz blockade, most have remained largely on paper, with the decisions having little effect on oil prices, apart from in July during a brief U.S.-Iran ceasefire that raised hopes Hormuz would reopen.
The contrast with 2019 is striking. Then, OPEC+ and U.S. President Donald Trump, during his first term, regularly clashed over oil prices, and OPEC+ decisions were closely watched by traders for their potential market impact.
At that time, the key question was how much oil OPEC+ chose to pump. Now, the focus is how much oil can physically be produced and exported amid a Middle East war.
One of the biggest price drivers this year has been a steep decline in Chinese oil imports. Since the war began, China has bought roughly 400 million fewer barrels of oil than during the same period last year.
The decline reflects a ban on fuel exports, lower refining output and the growing use of electric transport.
The trend further highlights China's growing role in balancing oil markets, a role once associated almost exclusively with OPEC+ as the world's swing producer.
China's weaker demand for oil has helped place a ceiling on prices this year. By contrast, its buying spree last year, which may have accounted for as much as half of global oil demand growth, helped underpin the market.
"They’ve become the swing demand centre," said June Goh, an analyst at Sparta Commodities.
(Editing by Dmitry Zhdannikov and Mark Potter)
