Jockeying in oil markets may strain Russia’s relations with Venezuela — and Iran.
As Russia pushes to find new buyers for its oil to skirt ever tougher Western sanctions, it is cutting into the market share of two of its allies — Iran and Venezuela — and setting off a price war that could hurt them all.

The competition for sales to Asia has already forced Venezuela and Iran to sharply discount their crude to try to hang onto the few available outlets for their own sanctioned exports, according to oil analysts and traders.

And although both Iran and Venezuela publicly remain close to Russia, experts expect that if the oil battle intensifies it will raise tensions with the Kremlin even as its leader, Vladimir V. Putin, is working to shore up his alliances. On Tuesday, his government announced he would make a rare trip outside the country next week to Tehran.