The US has authorised sanctions that include visa bans and the seizure of assets of Ukrainians and Russians involved in stoking Ukraine's ongoing crisis.
Barack Obama, the US president, issued an executive order and declared a state of emergency on Thursday, calling Russia's involvement in Crimea an "extraordinary threat" to US national security and foreign policy.
People who "undermine democratic processes and institutions in Ukraine, threaten its peace, security, stability, sovereignty, and territorial integrity and contribute to the misappropriation of its assets" will have any existing property and interests in the US blocked, Obama said.
We need to send a very clear message to the Russian government that what has happened is unacceptable and should have consequences.
At a press conference in Washington DC, the US president emphasised that these actions were in line with those of European allies.
"I am confident that we are moving forward together," he said.
The European Union announced that it would suspend talks with Russia on a wide-ranging economic pact and on a visa deal during a meeting in Brussels on Thursday.
The EU members of G8 also agreed to suspend preparations for a G8 summit in June in Sochi, according to Donald Tusk, Poland's prime minister.
And the bloc threatened further sanctions on Russia if Moscow refused to engage in talks to end the crisis in Ukraine.
Europe stopped short of imposing asset freezes and travel bans on Russian officials. EU exports to Russia in 2012 totalled $170bn and European banks have about $277bn in outstanding loans to Russia.
Al Jazeera's Simon McGregor-Wood, reporting from the EU meeting, said the bloc was divided on the issue of sanctions.
"There are significant splits with the Polish and Lithuanians and others wanting a far more aggressive approach to sanctions," McGregor-Wood said. "But as far as we know, the more moderate voices are urging caution and dialogue."
Poland, Lithuania and other eastern European countries located closer to Russia's borders pushed for a strong and united EU response, including meaningful sanctions. Germany, the Netherlands and others preferred defusing the crisis through diplomacy without alienating Moscow.
"We need to send a very clear message to the Russian government that what has happened is unacceptable and should have consequences," said David Cameron, Britain's prime minister.
|Possible impacts of sanctions on Russia
"Russia today is dangerous," said Dalia Grybauskaite, Lithuania's president. He gave warning that Moscow is seeking to expand its borders: "After Ukraine will be Moldova, and after Moldova will be different countries."\
Both the US and EU said further actions would be determined by Russia's decisions.
"They [sanctions] give us the flexibility to adjust our response going forward based on Russia's actions," Obama said.
Angela Merkel, Germany's chancellor, said the EU would go further if Russia adopted "further measures of destabilisation, or were to take measures of a military nature. I hope and trust this will not come to pass."