Russia continued to bear down on Ukraine's largest cities over the weekend, but Russian fighters bore stiff resistance from Ukrainians. Peace talks are set to take place between delegates of the two nations Monday on the Ukrainian-Belarusian border.
Still, President Vladimir Putin ordered his country's deterrence forces — including nuclear arms — be placed on high alert. That unnerved investors, concerned that the war could spill over to other countries outside of Ukraine.
Putin's threat came after the White House and several EU nations announced the expulsion of certain Russian banks from the SWIFT banking system Saturday evening. Removing some Russian banks from SWIFT could effectively disconnect them from the international financial system, hindering their ability to do global business.
But that action could hurt European countries' ability to buy Russian energy. Senior Russian lawmakers have said that shipments of oil, gas and metals to Europe would stop if the country's financial system is removed from SWIFT. Russia remains a key exporter of oil and natural gas for much of Europe, and immediate alternatives that could blunt rising energy prices from a reduction of Russian exports aren't obvious.
Some Western banks also have assets tied up in Russia, and cutting Russian banks off from SWIFT could sting.
Dow futures were down 400 points or 1.1%. S&P 500 futures fell 1.3%. Nasdaq futures were 1.3% lower.
The disruption to oil in particular is concerning to investors. Oil prices surged. Brent crude, the international benchmark, rose 4% to $101.80 a barrel. US crude rose 4.8% to $96 a barrel.