Leaders of the Group of Seven (G7) nations on Tuesday culminated a three-day summit emphasizing they were united in a commitment to back Ukraine for “as long as it takes” to expel Russia, though they stopped short of finalizing the centerpiece of new sanctions that would cap prices on Kremlin-backed oil.

Map of Europe

Members of the consortium of wealthy nations, which includes the United States, said they were committed to limiting Russian oil prices in an effort to kneecap the Kremlin’s ability to finance its invasion of Ukraine. The measure could also help curb prices of gasoline and other fuels derived from oil that surged amid the war and previous sanctions against Russia. Earlier penalties include U.S. and European Union (EU) embargoes on Russian oil imports.

The G7 leaders,...