Russian President Vladimir Putin brushed off an initial round of Western sanctions over the Ukraine crisis and defied warnings of stiffer punishment to come by taking another step toward annexing Crimea.
The Obama administration Monday enacted what it called the most comprehensive sanctions to hit Russia since the end of the Cold War. It targeted 11 Russian and Ukrainian officials, including some of Mr. Putin's top advisers and the ousted former president of Ukraine, Viktor Yanukovych, a close Kremlin ally.
The European Union followed by blacklisting 21 individuals. Unlike the U.S. it steered clear of Mr. Putin's inner circle, wary of ratcheting up the East-West confrontation. Business ties run deeper between Russia and Europe, although the landscape gets murkier as tensions climb.
"It's very powerful executive order and could be at the core of a much-broader sanctions regime against Moscow," said Mark Dubowitz of the Foundation for Defense of Democracies, a conservative think tank in Washington that has advised Congress on Iran sanctions.
Mr. Dubowitz said there is already discussion on Capitol Hill of legislation that would allow the White House to sanction any foreign firm doing business with any blacklisted Russian company or individual. The current sanctions only apply to American entities.
"This knock-on effect overseas has been the most powerful part of the Iranian sanctions," Mr. Dubowitz said. He noted that Iran's government has been virtually frozen out of the international banking system, and its oil exports halved.