Crude has been on the rise for weeks as Biden pushes his $1.9 trillion rescue package, which includes big cash handouts and a hike in the minimum wage.
Under the new curbs, authorities brought forward by three hours a nighttime curfew in metropolitan Athens, where about half of the country's population lives.
"It's people's lives. Real-life people are hurting and we can fix it," Biden said earlier. "When we help them we are also helping our competitive capacity," he said.