Vladimir Putin, the president of the Russian Federation, ordered an invasion of Ukraine on Monday after declaring the "independence" of two separatist regions of the country.
Russia has accused Ukraine of oppressing Russian-speaking populations in Donetsk and Luhansk, two regions in southeastern Ukraine. Putin on Monday said Russia would send "peacekeeping" troops into the separatist areas, which critics say is a brazen excuse to invade a sovereign neighbor state.
Russian-backed rebels in regions of Ukraine have called for separation since 2014, but in recent months Russia has placed more than 150,000 troops on its border with the country. In response, Ukrainian citizens have armed themselves in anticipation of the expected invasion.
A senior Biden administration official reportedly told journalists that Russia sending "peacekeeping" troops into Ukraine didn't necessarily constitute an invasion.
"We will observe and assess what actions Russia actually takes and respond," the official said.
Biden also spoke with Ukrainian President Volodymyr Zelensky in a call after the announcement from Putin.
President Joe Biden has warned that the United States would hit Russia with punitive economic sanctions if they invaded. Those sanctions are expected to be announced on Tuesday.
The United States agreed to defend Ukraine in 1994 after the country agreed to dismantle more than 5,000 nuclear weapons left over from the fall of the Soviet Union.
Putin has reiterated many times his belief that the fall of the Soviet Union was the worst geopolitical catastrophe of the 20th century. In his speech Monday, he said it was "madness" that former Soviet republics were allowed to leave the USSR.
Here's more about the decree from Putin:
Vladimir Putin declares two Ukraine regions independent www.youtube.com