The 120mm rounds are for the US M1 Abrams, the Pentagon said in a statement, referring to tanks that Washington has promised to Kyiv.

The density of uranium -- about 1.7 times that of lead -- helps such ammunition punch through heavy armor.

But depleted uranium is controversial due to its association with health problems such as cancer and birth defects in past conflicts, though the munitions have not been definitively proven to be the cause of these issues.

The United States has spearheaded the push for international support for Ukraine, quickly forging an international coalition to back Kyiv after Russia invaded last year and coordinating aid from dozens of countries.

Washington has promised Kyiv more than $43 billion in military assistance since Moscow launched its full-scale invasion of Ukraine in February 2022.