President Joe Biden has announced the US is sending a small number of high-tech, medium-range rocket systems to Ukraine to aid its forces as they struggle to stall Russian progress in the Donbas region.
According to two senior administration officials, the rocket systems are part of a new $700m (£553m) portion of security assistance for Ukraine from the US that will include helicopters, Javelin anti-tank weapon systems, tactical vehicles and spare parts.
Officials said the plan is to send Ukraine the High Mobility Artillery Rocket System, or HIMARS, which is mounted on a truck and can carry a container with six rockets.
The system can launch a medium-range rocket, which is the current plan, but is also capable of firing a longer-range missile, the Army Tactical Missile System, which has a range of about 190 miles (300 kilometres) and is not part of the plan.
It is believed that the US decision to provide the advance rocket systems will try to strike a balance between the desire to help Ukraine battle ferocious Russian artillery barrages while not providing arms that could allow Ukraine to hit targets deep inside Russia and trigger an escalation in the war.
In a guest essay published in the New York Times, Mr Biden confirmed that he has decided to "provide the Ukrainians with more advanced rocket systems and munitions that will enable them to more precisely strike key targets on the battlefield in Ukraine".
Mr Biden had previously said that the US would not send Ukraine "rocket systems that can strike into Russia", although any weapons system can shoot into Russia if it is close enough to the border.
According to the senior administration officials, the Ukrainians have assured US officials that they will not fire rockets into Russian territory.
One official noted that the advanced rocket systems will give Ukrainian forces greater precision in targeting Russian assets inside Ukraine.
Watch: Russia appears to use thermobaric weapons in Donbas.
The expectation is that Ukraine could use the rockets in the eastern Donbas region, where they could both intercept Russian artillery and take out Russian positions in towns where fighting is intense, such as Severodonetsk.
In his New York Times essay, Mr Biden added: "We are not encouraging or enabling Ukraine to strike beyond its borders. We do not want to prolong the war just to inflict pain on Russia."
Ukrainian President Volodymyr Zelensky has been pleading with the West to send multiple launch rocket systems to Ukraine as soon as possible to help stop Russia's destruction of towns in the Donbas.
The rockets have a longer range than the howitzer artillery systems that the US has provided Ukraine. They would allow Ukrainian forces to strike Russian troops from a distance outside the range of Russia's artillery systems.
"We are fighting for Ukraine to be provided with all the weapons needed to change the nature of the fighting and start moving faster and more confidently toward the expulsion of the occupiers," Mr Zelensky said in a recent address.
US and White House officials had no public comment on the specifics of the aid package.