The first shipment of assistance recently directed by President Biden to Ukraine arrived in Ukraine.
The first shipment of US military aid for Ukraine arrived in Kyiv on Wednesday, as tension continues to mount over Russia's troop build-up on the border.
The US embassy said some 90 tonnes of the "lethal aid" had arrived, including ammunition for "front line defenders."
The US embassy in Kyiv tweeted photos of a consignment it said had just arrived from the US, with "close to 200,000 pounds of lethal aid, including ammunition for the front line defenders of Ukraine".
The shipment demonstrated Washington's "commitment to helping Ukraine bolster its defenses in the face of growing Russian aggression", the embassy said on Twitter.
Top US and Russian diplomats agreed on Friday to keep talking in the standoff over Ukraine, even though their meeting produced no movement in the worst security crisis to emerge between Moscow and the West since the Cold War.
The delivery followed US Secretary of State Antony Blinken's visit to Kyiv this week, where he warned of a tough response if Russia was to invade the neighbouring country.
Moscow has denied any such plans.
Saturday's delivery marked the first part of a $200m security support package approved by US President Joe Biden in December.
Ukrainian Defence Minister Oleksiy Reznikov thanked the US for the aid.
Russia had seized Crimea from Ukraine in 2014 and the NATO chief has warned that fresh conflict in Europe could break out after an estimated 100,000 Russian forces have been positioned on the border.
Moscow has denied it is planning an invasion, but President Vladimir Putin has issued demands to the West which he says concern Russia's security, including that Ukraine be stopped from joining NATO.
He also wants NATO to abandon military exercises and stop sending weapons to eastern Europe, as this poses a threat to Russia's security.