The White House, along with the European Commission, France, Germany, Italy, the United Kingdom and Canada, announced Saturday evening that they would expel certain Russian banks from SWIFT, the high-security network that connects thousands of financial institutions around the world, pledging to "collectively ensure that this war is a strategic failure for (Russian President Vladimir) Putin."

The Society for Worldwide Interbank Financial Telecommunication was founded in 1973 to replace the telex and is now used by over 11,000 financial institutions to send secure messages and payment orders. With no globally accepted alternative, it is essential plumbing for global finance.

Removing Russia from SWIFT would make it much harder for financial institutions to send money in or out of the country, delivering a sudden shock to Russian companies and their foreign customers — especially buyers of oil and gas exports denominated in US dollars.

The United States and Germany have the most to lose if Russia is disconnected, because their banks are the most frequent SWIFT users to communicate with Russian banks, according to Shagina.

But the pain could be widespread. Senior Russian lawmakers have said that shipments of oil, gas and metals to Europe would stop.