Average gasoline prices, which had been falling for weeks, rose 4 cents a gallon Tuesday amid heightened tensions with Iran that pushed oil prices up more than 4 percent and that could portend even higher prices in coming weeks.

Tuesday’s increase came as Iran renewed threats to block a vital Middle East shipping route in the wake of Europe’s Iranian oil embargo that took effect Sunday. The embargo was put in place due to Iran’s nuclear program.

The price rise also comes amid a New York Times report that the U.S. has increased military reinforcements in the Persian Gulf and as Iran has launched war games in the region.

“The concern isn’t that Iran might sink a ship,” said Michael Lynch, president of Strategic Energy & Economic Research. “It’s for a longer conflict that will keep insurers wanting to stay away from the Gulf, which would cause a disruption of shipping that could last a few weeks. That’s a major disruption of the world’s oil.”

Combined with a big gain on Friday, oil has risen by nearly $10 per barrel in less than a week.