US President Joe Biden has called Russia's decision to commence a military operation in eastern Ukraine an "unprovoked and unjustified attack".
He said in a statement: "The prayers of the entire world are with the people of Ukraine tonight as they suffer an unprovoked and unjustified attack by Russian military forces.
"President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering. Russia alone is responsible for the death and destruction this attack will bring, and the United States and its Allies and partners will respond in a united and decisive way.
"The world will hold Russia accountable," Biden said.
"I will be monitoring the situation from the White House this evening and will continue to get regular updates from my national security team.
"I will meet with my G7 counterparts in the morning and then speak to the American people to announce the further consequences the United States and our allies and partners will impose on Russia for this needless act of aggression against Ukraine and global peace and security."
Biden said the US will coordinate with its Nato allies to ensure a strong, united response to deter any aggression against the alliance.
"Tonight, Jill and I are praying for the brave and proud people of Ukraine."
Australian Associated Press
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