The Biden White House on Friday announced an additional $270 million in security assistance for Ukraine, including four more mobile rocket launchers — a weapon that officials say has caused severe damage to Russian forces.

John Kirby, a National Security Council spokesperson, told reporters that the Biden administration will deliver four additional truck-mounted, multiple-rocket launchers — called High Mobility Artillery Rocket Systems, or HIMARS — bringing the number the United States has sent to 16.

Kirby said the United States will also send more HIMARS ammunition, as well as 36,000 rounds of artillery ammunition for howitzers already delivered to Ukraine. Those items will be drawn down from existing Defense Department stocks, Kirby said.

In addition, Kirby said, the Defense Department will provide Ukraine with up to 580 Phoenix Ghost tactical drones. Similar to the better-known Switchblade drone, the drones are capable of surveillance but can also be flown into targets and detonated on impact.

Lloyd Austin, the secretary of defense, and Gen. Mark Milley, chair of the Joint Chiefs of Staff, previewed the coming HIMARS delivery during remarks to reporters at the Pentagon earlier this week. Milley said that Ukrainian forces were “effectively employing these HIMARS, with strikes against Russian command and control nodes, their logistical networks, their field artillery near defense sites and many other targets.”

“These strikes are steadily degrading the Russian ability to supply their troops, command and control of their forces, and carry out their illegal war of aggression,” Milley said.

Kirby said that the new deliveries would bring the Biden administration’s total military assistance to Ukraine to $8.2 billion and that more aid packages would be announced in the coming weeks. “The president’s been clear that we’re going to continue to support the government of Ukraine and its people for as long as it takes,” Kirby said.

This article originally appeared in The New York Times.