The Pentagon will send four more High Mobility Artillery Rocket Systems (Himars) to Ukraine, US Secretary of Defence Lloyd Austin said on Wednesday, citing the weapon's effectiveness in countering Russia’s forces.
Mr Austin made the announcement as he hosted a virtual meeting for the so-called Ukraine Contact Group, a coalition of nearly 50 countries that are helping Kyiv.
A full new aid package will be rolled out later this week, the Pentagon chief said.
“The Ukrainians have been using [the Himars] so effectively," he said, noting the rockets had "made such a difference on the battlefield".
The new shipment brings the number of Himars provided to Ukraine to 16.
The weapon is a mobile unit that can simultaneously launch several precision-guided missiles. Russia also operates multiple-rocket launchers, but the Himars has a superior range and precision, with its rockets able to fly as far as 80 kilometres.
Longer-range rocket fire is seen as crucial as Russian and Ukrainian forces slug it out in a brutal artillery and missile fight across the relatively open terrain of the eastern Donbas region.
The US has trained more than 100 Ukrainian troops on operating the launchers.
“Our assistance is making a real difference on the ground,” Mr Austin said.
Nearly six months after the war began, Mr Austin said Russia had made a series of miscalculations, pointing to Moscow's failure to take Kyiv and most of the rest of Ukraine.
“Russia tried to topple the democratically elected government of Ukraine, and they failed. And then Russia retooled and thought it could easily seize the Donbas and they failed,” he said, blaming Russian President Vladimir Putin.
“Putin has consistently overestimated Russia's military prowess and he has consistently underestimated the power of a free people fighting to defend their homeland."
Russia insists the war, which it calls a "special military operation", is going according to plan and has threatened to target western shipments of weaponry to Ukraine, including the Himars.
The forthcoming US package will also include guided artillery ammunition, tactical vehicles and other urgent support, the Pentagon said.
The US has committed approximately $6.9 billion in security aid to Ukraine since Russia invaded Ukraine on February 24.
Charles Brown, US Air Force Chief of Staff General, told Reuters on Wednesday that Washington and its allies are examining possible training for Ukrainian pilots as part of a long-term effort to help Kyiv build a future Ukrainian air force.
Ukraine has sought to move away from its dependence on Russian aircraft by securing US fighter jets and training for its pilots on how to fly them. Ukraine's air force has publicly flagged its hopes for F-15s and F-16s.