(CBSDFW.COM) — Americans may feel a hit at the gas pump following a U.S. military strike ordered by President Donald Trump that killed a top Iranian general.

Brent crude, a global benchmark, gained as much as 4.2 percent Friday, hitting $69.50. West Texas Intermediate (WTI) prices also spiked more than 4 percent, reaching as high as $64.09.

Both are on track for their biggest daily gains in about a month and their highest prices since September, when Iran attacked Saudi oil facilities.

The news also dampened Wall Street’s euphoric start to 2020, with the Dow Jones industrial average falling more than 300 points at the open. An hour later, the DJIA was down 210 points, or 0.7 percent, to 28,659.

General Qasem Soleimani, commander of the Quds Force of Iran’s Islamic Revolutionary Guards Corps, was killed Friday in the strike at Baghdad International Airport.

The Pentagon said Soleimani was “actively developing plans to attack American diplomats and service members” and that the strike was aimed at “deterring future Iranian attack plans.”

The attack was expected to draw Iranian retaliation in the Middle East, which is home to major oil producing countries and key energy supply routes.

About 20 percent of oil traded worldwide goes through the Strait of Hormuz, where the shipping lane is only two miles wide and tankers have come under attack this year.

Oil prices spiked more than 14 percent in September after coordinated attacks on Saudi Arabian oil production facilities, CNN Business reported. But prices pulled back quickly after Saudi officials said the kingdom would rely on reserves to keep exports stable.