NEW YORK>> Brent oil shot to its highest price since May after increased fighting in the Middle East on Thursday threatened to slow the global flow of crude. At the same time, sharp drops for two of Wall Street’s most influential companies, Alphabet and Tesla, yanked the U.S. stock market to its worst loss in a month.

The S&P 500 fell 1.2% and is on track for its first back-to-back weekly loss since March. The Dow Jones Industrial Average dropped 506 points, or 1%, and the Nasdaq composite sank 2.2%.

Stocks fell under the pressure of rising oil prices, which raise costs for businesses and erode their customers’ ability to spend. The price for a barrel of Brent crude oil, the international standard, jumped 7% to settle at $100.69.

It touched $102 during the day, the highest price since May for the most actively traded Brent contract in the market. The cause: attacks on two Saudi oil tankers in the Red Sea. That threatens another avenue that oil companies use to move their crude from the Middle East to customers worldwide, along with the Strait of Hormuz.

It was just a few weeks ago that Brent had dropped below $72 per barrel, roughly back to where it was before the United States and Israel attacked Iran to begin their war, on hopes that a wind-down in the war would fully reopen the Strait of Hormuz.

The jumps in oil prices will worsen inflation, just when it had begun to decelerate by more than economists expected. That in turn could push the Federal Reserve and other central banks to raise interest rates, which would slow economies and undercut prices for stocks and other investments.

Higher oil prices pushed the yield of the 10-year Treasury up to 4.69% from 4.67% late Wednesday and from just 3.97% before the war with Iran began. That’s a significant increase, and it’s already brought long-term U.S. mortgage rates to their highest levels in nearly a year.

Gasoline prices tend to follow oil prices higher, and a gallon of regular costs an average of $4.09 across the United States, according to AAA.

All told, the S&P 500 fell 90.66 points to 7,408.30. The Dow Jones Industrial Average dropped 506.93 to 51,711.65, and the Nasdaq composite sank 553.21 to 25,137.69.