WASHINGTON — The U.S. and Russian presidents imposed sanctions on each other's top aides and other government officials Thursday as the dispute over Crimea intensified and the White House worried publicly that Moscow might be positioning its military to seize more of Ukraine.
Denouncing Russia's annexation of Crimea, President Obama said the Treasury Department would freeze any U.S. assets of 20 prominent Russians — including several officials close to President Vladimir Putin, some of the country's wealthiest businessmen — and a Moscow bank that gives financial support to the Russian leadership.
Saying the "world is watching with grave concern," Obama also warned that he was prepared to take far harsher measures if Russian troops on maneuvers cross farther into southern or eastern Ukraine. Obama said he had signed an executive order to authorize penalties against "key sectors of the Russian economy" if necessary, warning that those sanctions could be "disruptive to the global economy." Obama has ruled out U.S. military action.
Putin, who has long had a frosty relationship with Obama, responded swiftly by banning nine U.S. lawmakers and White House officials from entering Russia, according to the Russian Foreign Ministry. The list includes House Speaker John A. Boehner (R-Ohio), Senate Majority Leader Harry Reid (D-Nev.), Sen. John McCain (R-Ariz.) and three top Obama aides.
Several of the U.S. lawmakers said they were honored to be singled out, and at least one Russian laughed off the U.S. punishment.
"Proud to be included on a list of those willing to stand against Putin's aggression," Boehner said on Twitter. "I guess this means my spring break in Siberia is off," quipped McCain, who visited Ukraine last week.
The unusual back-and-forth came after the State Duma, the lower house of the Russian parliament, voted 443 to 1 to admit Crimea, defying Western complaints that it was approving what Washington and its allies consider an illegal land grab.
In Crimea, Russian flags flew over captured Ukrainian military bases and ships. Banks were closed. The Ukrainian Defense Ministry in Kiev, the capital, said it was preparing to evacuate an estimated 25,000 military personnel and their families from Crimea. Officials in Kiev and Moscow warned of possible restrictions on visas and trade in goods including gas and livestock.
The Standard & Poor's credit-rating agency downgraded its rating of Russia to "negative," warning of a possible outflow of capital and reduced investment. Whether that will affect Putin's thinking is unclear. Polls show most Russians support his actions so far, and dissent has been limited.
On Monday, Washington and the 28-nation European Union jointly imposed a first round of sanctions, travel bans and asset freezes against about two dozen mid-level Russian and Ukrainian officials.
EU leaders meeting in Brussels on Thursday said they had agreed to blacklist 12 more Russian officials.
In theory, Europe is in a stronger position than America to punish Russia's ruling elite because many of Russia's richest families and institutions own property or investments across the continent.
But Europe is far more reliant on Russian oil and gas, and leaders fear further disruptions to their fragile economies after years of a debilitating regional debt crisis.
German Chancellor Angela Merkel, the continent's most powerful leader, signaled that Berlin was not prepared yet to seek economic and financial sanctions. She has said that might happen if Russia destabilizes regions beyond Crimea — comments widely interpreted to mean eastern and southern Ukraine.
But Merkel said leaders had directed the European Commission to start preparing the ground for them.
Merkel told German lawmakers that the Group of 8 forum, formed when Russia joined seven economically advanced nations, was no longer a viable arrangement. A G-8 summit that was to take place in Sochi, Russia, hosted by Putin, is now on ice.
So is an EU-Russia meeting scheduled for this year, French President Francois Hollande said.
Some political analysts say Putin has banked on the EU putting its commercial interests above principle on Crimea. They describe the Russian leader as skeptical that European leaders are willing to see their economies and their own political fortunes suffer.
Swedish Prime Minister Fredrik Reinfeldt acknowledged those concerns.
"We need to prepare ourselves for different kinds of sanctions, because there is a worry that the provocations in Ukraine will continue and also expand to other parts of Europe," he told reporters in Brussels. "We need to prepare ourselves, and that means, of course, hurting ourselves in a way."