Oil futures ticked slightly lower early Tuesday, a day after a fresh round of U.S. sanctions aimed at curtailing Iran’s crude exports provided a modest lift.

Oil prices rose for a second day on Tuesday as fresh U.S. sanctions imposed on Middle Eastern producer Iran increased concerns supply might tighten and as global refining margins remained strong. Brent crude futures rose 15 cents,

The U.S. on Monday imposed sanctions on dozens of people and oil tankers across China, the United Arab Emirates, India and other jurisdictions for allegedly helping to finance Iran and its support for militant groups that launch attacks against the U.