Last Middle East oil shipment reportedly reaches SoCal. Here's what that means for gas prices

LONG BEACH, Calif. (KABC) -- Gas prices are at a four-year high and experts are warning they could climb even higher.

The final oil tanker from the Middle East has docked in Long Beach, putting the region's supply chain under pressure. According to a report from the Los Angeles Times, it's the last shipment from the Strait of Hormuz to reach California.

After that tanker leaves, it could be weeks or potentially months before the next one arrives from the Middle East.

"The war in Iran and the closing of the Strait of Hormuz has actually been buffered by the fact that all of these tankers were at sea at the time that the Strait of Hormuz closed," said UCLA Professor Michael Ross. "So all of that supply has still been making its way to consumers. This is the last shipment of that supply that was keeping prices relatively stable. So that should worry us."

With that key shipping route disrupted by war, refineries are racing for other sources as local gas prices top $6 a gallon in some areas. The average price in California is $6.11, according to AAA.

The war in Iran has already driven gas prices up over the last two months, but experts say the worst is yet to come.

Meanwhile, U.S. forces will begin supporting "Project Freedom" in the Strait of Hormuz at the direction of President Donald Trump, beginning on Monday.

The mission is intended "to restore freedom of navigation for commercial shipping through the Strait of Hormuz," CENTCOM said.

The U.S. military role will be to extend a U.S. defensive umbrella over ships seeking to leave or enter the Strait of Hormuz, a U.S. official told ABC News. Project Freedom is not about providing escorts to ships, the official said.

"U.S. military support to Project Freedom will include guided-missile destroyers, over 100 land and sea-based aircraft, multi-domain unmanned platforms and 15,000 service members," CENTCOM said in its statement.

ABC News contributed to this report.