What’s more, the grade of Russia’s main export oil, Ural Blend crude, is similar to Iran’s and has already been in greater demand as an alternative to Iranian oil for European refineries.

That’s why the price of Ural Blend has risen even faster than global prices generally. In December, it traded at a $2 discount to Brent oil from the North Sea. That difference is now gone. Both grades are now trading for about $119.50 a barrel, energy analysts say.

The six nations Iran threatened to cut off Wednesday were, in descending order of the size of their purchases: Italy, Spain, France, the Netherlands, Greece and Portugal. Tehran did not explain why it selected those countries, while ignoring even bigger oil users like Germany.

But all six were already planning to stop buying Iranian oil this summer, anyway, as part of an embargo the 27-nation European Union agreed to last month, to begin in July. At its recent peak, Europe was buying 500,000 to 660,000 barrels of Iranian oil a day, according to PFC Energy.

If the European sanctions do take effect then, oil prices could rise further — by as much as $7 to $13 a barrel above where they are now, in the view of Wood Mackenzie, an oil consultancy based in Edinburgh.

And even if oil prices later fall, Russia’s natural gas monopoly, Gazprom, would continue to benefit for a while. Russian gas prices in Europe, Gazprom’s biggest export customer, are linked to the price of oil under long-term contracts that are adjusted twice annually, based on average oil prices over the previous six months. So even if oil prices decline, Gazprom’s gas prices would remain high in the second half of the year.