Challenged to respond to the invasion, Biden said the United States and its NATO allies replied: "Yes, we would stand up for sovereignty.
Biden went on to say that "there should be no doubt: Our support for Ukraine will not waver, NATO will not be divided, and we will not tire."
Biden rejected Russia's assertion that Western allies were seeking to control or destroy Russia through their backing of Ukraine.
In two speeches last September, Putin indicated that he would, if needed, use nuclear weapons to defend Russia.
The biggest land war in Europe since World War Two has displaced millions, left Ukrainian cities, towns and villages in ruins and disrupted the global economy.