Stocks extend their rout as the Ukraine war and its economic fallout intensify.

“We are now in very active discussions with our European partners about banning the import of Russian oil to our countries while, of course, at the same time, maintaining a steady global supply of oil,” Mr. Blinken said on Sunday on “Meet the Press” on NBC.

A precipitous drop in oil and natural gas supplies from Russia would create major problems for both industrial users and consumers. Cutting off Russian oil would force many refineries that normally process it to find other sources.

Although oil is a relatively flexible commodity, there are many grades of crude, and a refiner cannot always substitute one for another. Washington’s sanctions on Venezuelan crude, for instance, led refiners in the United States to buy more Russian oil as a substitute, raising import levels. On Saturday, Shell, Europe’s largest oil company, said it had bought Russian crude oil because supplies from “alternative sources would not have arrived in time to avoid disruptions to market supply.”

Investors had already been nervous about inflation, which has been the highest in decades in the United States and Europe after the pandemic shut factories and left supply chains snarled.

Economists expect the Consumer Price Index to show on Thursday that prices in the United States rose 7.9 percent in the year through February. And that reading was taken before the effects of the war were really starting to be felt. Gas prices, for example, rose to their highest level in the United States since 2008 on Monday: $4.06 a gallon, according to AAA, up 45 cents from a week ago.

Central banks have started to move aggressively to raise interest rates as they shift their focus from supporting economic growth to combating inflation. The end of easy money and the lure of higher rates — which make riskier investments less attractive — had already caused stocks to decline even before Russia’s invasion.

But the war’s financial fallout is hitting Europe the hardest. Natural gas is less flexible than oil, and Europe is much more dependent on it as a fuel. Prices for natural gas in Europe were already many times what they were a year ago and have been spiraling even higher, touching 345 euros per megawatt-hour on Monday before paring back to €215, an 11.7 percent gain.