President Barack Obama announced new economic sanctions against key sectors of the Russian economy. It's the latest move by the United States to force Russian President Vladimir Putin to stop supporting Ukrainian rebels.
The new round of U.S. sanctions targets Russia's energy, weapons, and finance sectors, including big banks.
"It didn't have to come to this," Obama said. "It does not have to be this way. This is a choice that Russia and President Putin in particular has made."
The sanctions came only hours after the European Union imposed its own penalties against Russia -- the EU's toughest yet. They're all meant to pressure Putin to stop backing the rebels that control eastern Ukraine.
"We now have clear evidence of artillery and rocket fire from Russia into Ukraine, and while the Russians have said that they want to de-escalate the conflict, their actions have not shown a shred of evidence that they really have a legitimate desire to end the violence and end the bloodshed," said Secretary of State John Kerry.
The United States and European Union blame Russian-supported separatists for the chaos in eastern Ukraine and for shooting down Malaysia Airlines Flight 17 and killing 298 people. The plane flew over rebel-controlled territory.
Obama said Russia is building up its forces on the Ukrainian border and supplying the separatists with artillery and other military equipment.
However, as tensions rise between the United States and Russia, the president maintains it's not a new Cold War.
"What it is is a very specific issue related to Russia's unwillingness to recognize that Ukraine can chart its own path," the president said.
Meanwhile, Ukraine's president declared today a unilateral ceasefire around the Flight 17 crash site. Each time international experts have tried to reach the wreckage, they turn back because of the increasing violence between Ukrainian troops and pro-Russia rebels.
A home for the elderly, a school and several apartment blocks have been caught in the escalating fighting -- adding to a rapidly-growing civilian death toll.