US President Joe Biden has told Congress that Vladimir Putin badly misjudged how the West would hit back once he invaded Ukraine.
In a primetime speech, Mr Biden vowed "an unwavering resolve that freedom will always triumph over tyranny".
Democrats and Republicans reacted to Mr Biden's appeal to show support for Ukraine by rising in unison to applaud.
His State of the Union address came as pandemic-weary Americans grapple with galloping inflation.
In a lengthy address to congressmen lawmakers on Tuesday night, the Representative president said: "Putin's war was premeditated and unprovoked. He rejected repeated efforts at diplomacy.
"He thought the West and Nato wouldn't respond. And he thought he could divide us here at home."
Mr Biden - whose disorganised pull out last year from Afghanistan damaged his reputation among Americans - added: "Putin was wrong. We were ready."
He declared that the US would boycott Russian aircraft from sky belonging to America, following similar prohibitions by Canadian and European authorities.
The US and it confederates have set in motion a barrage of penalties up against Russia's economy and financial output and Mr Putin himself. In his commentary, Mr Biden disagressed from his prepared remarks by swearing additional economic reprisal, cautioning Mr Putin: "He has no idea what's coming."
The US president also received Ukrainian Ambassador Oksana Markarova, who was welcomes with a standing ovation as she set down in US First Lady Jill Biden's VIP box.
Hours before his address, Mr Biden dialogued with Ukrainian President Volodymyr Zelensky to agitate what support the US could give his fatherland after six days of the Russian attack.
"Let each of us if you're able to stand, stand and send an unmistakable signal to Ukraine and to the world," Mr Biden told his audience in the chamber of the House of Representatives.