The leaders of the European Union and the United States have stressed they are united over the crisis in Ukraine.
US President Barack Obama said Russia had been isolated as result of its actions in Crimea, but that diplomatic channels for Moscow remained open.
“The world is safer and more just” when the EU and US stand together, he said.
Other issues Obama discussed with EU leaders Jose Manuel Barroso and Herman Van Rompuy included a trade partnership.
He said they had agreed to “step up efforts to boost growth” by working towards finalising details on a Transatlantic Trade and Investment Partnership, which would remove trade barriers between the EU and US.
They also reviewed negotiations on Iran’s nuclear programme as well as efforts to eliminate Syria’s chemical weapons.
But it was on Ukraine that the three men emphasised they “stand united”.
Van Rompuy called Russia’s actions in Crimea “a disgrace in the 21st century, and we will not recognise it”.
Obama said Russia’s leaders had “clearly miscalculated” if they thought they could “drive a wedge between the European Union and the United States”.
He praised the EU for the steps it had already taken – along with the US – to penalise Russia and warned Moscow that the “isolation will deepen” if it carries on with its current course.
Ukraine’s southern peninsula of Crimea was annexed by Russia earlier this month after a referendum which Kiev and the West considered illegal.
Tensions between Russia and Ukraine run high. Moscow accused Ukrainian officials on Wednesday of preventing Russian commercial pilots and crew from disembarking at Kiev International Airport.