The munitions are highly effective against armoured targets such as tanks, White House National Security spokesman John Kirby said this week.
Depleted uranium rounds are denser and are also heavier than normal tank rounds, he said.
The $175 million security assistance package is part of a $1 billion tranche of US aid for Ukraine that Secretary of State Antony Blinken announced on Wednesday during a visit to Kyiv.
The 120mm depleted uranium shells can be fired from the US Abrams M1 tanks that the Pentagon has shipped to Ukraine.
“We want to make sure that the Ukrainians can be as effective as possible in this counter-offensive,” Mr Kirby said. “And it’s our belief that depleted uranium rounds will help them be more effective on the battlefield.”
Possible long-term risks
The UN describes depleted uranium – which is about twice as dense as lead – as a toxic heavy metal that is the main by-product of uranium enrichment.
While investigations are ongoing, there have been increased fears over possible adverse health and environmental effects caused by the use of depleted uranium munitions.
Ammunition containing depleted uranium explodes on impact and releases uranium oxide dust in the air, according to the UN Office of Disarmament Affairs.
Nato used depleted uranium munitions in the bombing of the former Yugoslavia in 1999 and the US used them in massive quantities in the 1990 and 2003 Gulf wars.
Iraqi doctors have blamed depleted uranium for increased cancer rates in some parts of the country.
“Depleted uranium rounds in our scientific studies found – including by the CDC [US Centres for Disease Control and Prevention] – pose no radioactive threat,” Mr Kirby said.
“They are simply denser than more conventional tank rounds, but there’s no carcinogenic or radioactive threat posed by depleted uranium rounds.”
He added that other countries, including Russia, have used them.
Mr Kirby said the materiel the US is sending Ukraine has evolved to meet changes since Russia's invasion in February 2022.
Since then, the Biden administration has pledged $43 billion in military support for Kyiv, including tanks, cluster ammunition and a wide range of weapons systems.