Potential showdown in eastern Syria over IS-held territory

FILE - In this July 26, 2017 file photo, U.S.-backed Syrian Democratic Forces fighters walk past destroyed shops where they fight against Islamic State group militants, on the eastern side of Raqqa, Syria. As U.S.-allied fighters hurtle down the eastern banks 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 IS. (AP Photo/Hussein Malla, File)
FILE - This file photo released Monday, Sept 4, 2017 by the Syrian official news agency SANA, shows Syrian troops and pro-government gunmen standing on pickup trucks mounted with heavy machine-guns, in the eastern city of Deir el-Zour, Syria. As U.S.-allied fighters hurtle down the eastern banks 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. (SANA via AP, File)
FILE - In this July 22, 2017 file photo, Arab and Kurdish fighters with the U.S.-backed Syrian Democratic Forces (SDF), move to the front line to battle Islamic State group militants, in Raqqa, Syria. As U.S.-allied fighters hurtle down the eastern banks 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 IS. (AP Photo/Hussein Malla, File)

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.