BEIRUT — As U.S.-allied fighters hurtle down the eastern bank of the Euphrates River, a showdown could ensue between the U.S. and Russia, whose allies are racing to take over the same strategic oil-rich territory from the Islamic State group.

While the two sides will likely avoid a direct confrontation, the capture of Raqqa by the U.S.-backed forces, followed by their swift seizure of Syria’s largest oil field from IS, has irked Damascus, which needs the oil to boost its flagging economy.

As the rival international coalitions compete to defeat the militants and snap up oil and gas fields, the Russian military has issued a stream of angry statements, accusing the U.S. of colluding with the Islamic State and other extremist groups in a bid to stymie the government’s advances.

Both the U.S. and Russia have embedded special forces with their respective partners and are supporting their advances with aggressive airstrikes. They have so far avoided any significant confrontations by maintaining talks and a hotline intended to prevent midair and ground incidents.

Ryan Dillan,  spokesman for the U.S.-led anti-IS coalition, said contacts with Russia were continuing to avoid friction on the ground around Syria’s Al-Omar oil field, which was seized by the Kurdish-led Syrian Democratic Forces on Sunday. But he indicated the coalition was prepared for any possibility.