The aid includes additional rockets for the High Mobility Artillery Rocket Systems, or HIMARS, as well as thousands of artillery rounds, mortar systems, Javelins and other ammunition and equipment.
The announcement comes as analysts warn that Russia is moving troops and equipment to southern port cities to stave off a Ukrainian counteroffensive.
“At every stage of this conflict, we have been focused on getting the Ukrainians what they need, depending on the evolving conditions on the battlefield,” Colin Kahl, undersecretary of defense for policy, said.
Monday’s package allows the US to deliver weapons systems and other equipment more quickly since it takes them off the Defense Department shelves.
For the last four months of the war, Russia has concentrated on capturing the Donbas region of eastern Ukraine, where pro-Moscow separatists have controlled some territory as self-proclaimed republics for eight years.
Russian forces have made gradual headway in the region while launching missile and rocket attacks to curtail the movements of Ukrainian fighters elsewhere.
Mr Kahl estimated that Russian forces have sustained up to 80,000 deaths and injuries in the fighting, though he did not break down the figure with an estimate of forces killed.
He said the Russian troops have managed to gain “incremental” ground in eastern Ukraine, although not in recent weeks.
“But that has come at extraordinary cost to the Russian military because of how well the Ukrainian military has performed and all the assistance that the Ukrainian military has gotten.
And I think now, conditions in the east have essentially stabilised and the focus is really shifting to the south.”
The US and allies still are evaluating whether to supply aircraft to Ukraine, Kahl said. It’s “not inconceivable that western aircraft down the road could be part of the mix,” he said.