In his speech to Congress, Volodymyr Zelensky compared Putin to Hitler and said that Ukraine needed additional weaponry.
Standing ovations welcomed the war commander as he confidently asserted that despite Putin's invasion, Ukraine remained "alive and kicking."
Zelensky invoked former US President Franklin D. Roosevelt, who held office from 1933 to 1945, and the fight to free Europe from Nazi rule in a stirring address at the Capitol.
He declared: "Brilliant Ukrainian warriors are doing the same this Christmas, much as the heroic American soldiers who lost their lives and resisted Hitler's armies during Christmas of 1944."
Zelensky pleaded with senators to continue contributing to the military effort against Russia to increase US support for Kyiv.
"Your money is not charity," he said while wearing khaki fatigues, "it is an investment in the world security and democracy that we manage most responsibly."
However, the comedian-turned-president said that artillery was "not enough" and that the US might hasten Ukraine's victory against Moscow.
He said: "We have artillery, sure, thank you, in English. Does it suffice? Actually, no.
"More guns and ammunition are required to make sure Bakhmut is not only a bastion that slows down the Russian force, but that the Russian army withdraws entirely.
Russia could halt its assault if it so desired. It happens as Congress completes a fresh package of emergency aid to Ukraine worth $45 billion, on top of the $50 billion already delivered this year.
Another $1.85 billion in military assistance for Ukraine, including a Patriot air defense system to help it fend off Russian missile barrages, was also presented by Joe Biden on Wednesday.
However, several Republicans have voiced worries about the cost.
Starting next month, they may refuse to accept billions of dollars in military assistance.
Zelensky, on the other hand, got a lot of applause on Wednesday when he said that Ukraine would "never give up" and warned that the fight was about more than just his country's future.
This war cannot be disregarded in the hopes that the ocean or another barrier would provide security, he added.
Zelensky praised the US for its assistance and said that speaking to Americans was a "privilege."
"Speaking to you and all Americans in the US Congress is a huge honor for me, the speaker said.
"Despite all dire predictions, Ukraine did not collapse. Ukraine is still thriving.
"In the fight for the hearts and minds of the world, we vanquished Russia."
The Russian people "will have a chance to be free only when they overcome the Kremlin in their imaginations," Zelensky said.
"Yet the conflict continues, and we must overthrow the Kremlin on the battlefield," the war's commander told Congress.
"These wars aren't only for land; they're also for the lives, freedom, and security of Ukrainians and every other country that Russia wants to subjugate.
"This conflict will determine the environment in which our offspring, followed by their offspring, will dwell.
It will determine if there will be a democracy for all Americans and Ukrainians.
In addition, Zelensky emphasized to the audience that Russia has an "edge" in terms of weapons, aircraft, and ammunition.
He concluded by presenting the Congress with a Ukrainian flag that had been provided to him by Bakhmut frontline fighters.
Zelensky went to the war-torn city the day before landing in the US.
After Zelensky's first overseas travel since Putin's invasion in February, Biden and his wife Jill welcomed him to the White House.
In 2023, when Zelensky made his first international trip during a conflict, the US president stood beside him to encourage the public to continue backing Kyiv.
"As we enter the New Year, the American people and the rest of the world must hear directly from you, Mr. President, about the struggle in Ukraine and the need of being together until 2023," added Biden.
The US president stated that he had never seen NATO or the EU as unified as they were in their support of Ukraine.
"We are talking about sanctions and legal pressure on the terrorist nation Russia," Zelensky stated.
Before that, the Ukrainian president honored Biden with a medal donated by a captain of a HIMARS rocket regiment and thanked him for his assistance in gaining support.