EXPLAINER: A look at West's toughest sanctions yet on Russia

The United States has joined European allies in dramatically escalating financial penalties against Russia over its invasion of Ukraine

WASHINGTON -- The United States joined European allies Saturday in dramatically escalating financial penalties against Russia over its invasion of Ukraine, after the West’s initial rounds of sanctions failed to deter Russian President Vladimir Putin in his military offensive.

Two of the key new measures target the heart of Russia's financial system, its Central Bank, and cut an unspecified number of Russia's banks off from the SWIFT financial network. SWIFT is a vital element of global commerce and banking that moves money from bank to bank around the world.

U.S. and European officials made clear they still were working on implementation of the sanctions, and said they would take care not to impact European purchases of Russian natural gas.

U.S. officials said the moves would send Russia's ruble currency crashing in value, and intensify its isolation financially. It's the latest and toughest in days of new sanctions since Russian forces moved into Ukraine late last week.