US Secretary of State Antony Blinken and Secretary of Defense Lloyd Austin pledged more than $700 million in direct and indirect military assistance to Ukraine.
The pledge was made during their visit to Kiev - the first of this level by an American since Russia began its invasion of Ukraine on February 24.
About half of the money will go to Ukraine, while the rest will be shared between NATO members and other regional allies.
In addition, the US will sell Kiev ammunition worth $165 million.
The administration of US President Joe Biden has already allocated several billion dollars in military and economic aid to Ukraine, including another $800 million on April 21.
US officials reiterated that the aid does not imply direct US involvement in Ukraine.
"The president has been very clear: there will be no American troops fighting in Ukraine," a defense official told US media.
Blinken, speaking to reporters near the Polish-Ukrainian border, said he and Austin traveled by train from Poland to Ukraine.
He said the visit to Kiev was an opportunity to directly demonstrate "our continued support for the Ukrainian Government."
Austin, on the other hand, said the visit to Kiev was "very productive."
He said he believes Ukraine can win the war "if it has the right equipment."
The two American officials also met with Ukrainian Foreign Minister Dmytro Kuleba, Defense Minister Oleksiy Reznikov, and Interior Minister Denys Monastyrsky.
Their trip was also used as an opportunity to announce that the United States Embassy in Kiev will begin reopening this week.
The two American officials also mentioned the name of American diplomat, Bridget Brink, as the new US ambassador.
Brink, who is currently ambassador to Slovakia, will fill the position in Kiev, which has been vacant since early 2020, when Donald Trump was president of the United States. US media reports that the administration of President Joe Biden will officially appoint her on Monday.
The US embassy in Kiev has been closed since the outbreak of war, while a temporary office has been relocated to neighboring Poland.
In another development, the British newspaper, the Financial Times, reported on April 24 that Russian President Vladimir Putin appears determined to occupy as much Ukrainian territory as possible, abandoning peace talks.
The Financial Times said it cited three people well-informed about the Russian president's conversations.
Putin has told people involved in efforts to end the conflict that he sees no prospect of a solution, the newspaper reported.
On the ground, Russian forces are continuing attacks in the east, including on the besieged city of Mariupol, the Ukrainian military said.
The General Staff of the Ukrainian Armed Forces said that the Russians have been firing on Ukrainian positions along the entire line of contact.
He also said that the Russian army has intensified its offensive operations in the direction of the cities of Severodonetsk, Kurakhiv and Popasna.
Ukrainian authorities put the number of casualties in the war in the tens of thousands, although these figures cannot yet be independently verified.
The number of displaced people from Ukraine, meanwhile, has exceeded five million./REL
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