A view of the European Commission building in Brussels, on March 23, 2026. Photo: JPix/NurPhoto via Getty Images

The closure of the Strait of Hormuz, a vital waterway between Iran and Oman, has affected 20 per cent of global oil flows, threatening shortfalls in some European refineries. That has prompted some countries to consider emergency export restrictions, with Hungary and Slovakia moving last month to ban or restrict oil flows to foreigners.

The worry is that more countries will follow suit. At a meeting on Friday, the EU executive told national energy officials to refrain from cross-border export restrictions within the EU after a number of countries warned their refineries faced supply constraints by next month, according to two people familiar with the matter. The fear is that it could lead to reduced production of critical refined products, the people added.

The countries that raised the concerns included France, Italy, Hungary and Slovakia, the people said. Spokespeople for those countries did not respond to POLITICO's requests for comment. Neither did the Commission.

The warning reflects growing unease around the security of the EU's supply of petroleum and petroleum derivatives that once flowed through the strait, which includes 40 per cent of its jet fuel and diesel imports. The airplane industry is particularly concerned, with Ryanair CEO Michael O’Leary warning that his airline could cancel up to 10 per cent of flights through May, June and July if the war continues deep into the summer.

While the EU imports relatively little crude oil from the Strait, over 95 per cent of the oil the bloc imports comes from abroad. That could further limit refineries' access to oil as increasing global competition for the fossil fuel tightens supply and raises prices — particularly in countries most exposed to the Gulf, which include Poland, Italy, Greece, the Netherlands, Lithuania, Bulgaria and France, according to data from trade intelligence firm Kpler. According to one national official, some multinational refineries with operations in exposed countries are already "struggling."

Asian refineries have already cut their processing by 2.7 million barrels a day since March, the International Energy Agency said in its monthly oil market report, published Tuesday.

While European refineries have yet to publicly broadcast operational difficulties of their own, "if the situation goes on for a few more weeks we'll get there, because the Asians will be scrambling for physical barrels wherever they come from, and that means they will be less available for Europeans," said Homayoun Falakshahi, an oil analyst at Kpler.

"If the war continues, and if the Strait of Hormuz isn't reopened, definitely it will happen, it's a question of when if not if."

The IEA echoed that point, noting that "increased competition for Atlantic Basin supplies has significantly curtailed the availability of prompt supplies and compressed margins," risking shortfalls by May. That's especially true as the last tankers bearing oil from the Strait of Hormuz arrive on European shores this week.

However, Kpler downstream analyst Sumit Ritolia cautioned that refiners might be likely to optimize their operations first before carrying out production cuts outright, since margins are still relatively healthy.

Early birds

A number of countries reacted to these growing pressures well ahead of others, moving to restrict fuel exports within days of the outbreak of the war. In early March, Hungary explicitly banned oil exports, highlighting the risk of supply shortages that it said had been compounded by fire damage to a major refinery on the Danube River and the closure of the Soviet-era Druzhba pipeline, a key source of Russian oil for the country.

Slovakia, which was also dependent on the Druzhba conduit, moved to impose higher prices for motorists with foreign license plates, drawing swift condemnation from the Commission.

The EU is particularly concerned to avoid measures that could disrupt the single market, according to one of the people. Last month, the EU's energy chief, Dan Jørgensen, warned explicitly against policies that limit the "free flow of petroleum products" across the bloc, according to a letter first seen by POLITICO.

The call for restraint comes after Jørgensen urged countries to encourage citizens to curb energy use, especially in the transport sector.