Russia publicly denounced the Biden administration’s decision to send depleted uranium munitions to Ukraine as a “criminal act” on Thursday.

“This is not just an escalatory step, but it is a reflection of Washington’s outrageous disregard for the environmental consequences of using this kind of ammunition in a combat zone,” Russian deputy foreign minister Sergei Ryabkov said.

On Wednesday, the Biden administration announced it would send the divisive ammunition for the first time to help Ukraine in its ongoing counteroffensive against Russia. The antitank rounds, which are used to pierce through a tank’s armor, are included in a $175 million aid package.

The 120 mm shells are intended for 31 M1A1 Abrams tanks that the U.S. will deliver to Ukraine by the end of the year.

Although incapable of producing a nuclear reaction, depleted uranium is controversial because it poses health risks to those who come into contact with it or inhale its dust.

The toxic chemical, which is derived from the uranium-enrichment process needed to create nuclear weapons, can make people sick and poison groundwater and soil, according to the International Coalition to Ban Uranium Weapons.

Kremlin official Dmitry Peskov said introducing the depleted uranium to Ukraine could be “very bad news,” not just for Russia. When the U.S. used the rounds in the former Yugoslavia during the late 1990s, citizens in those areas suffered from “a galloping rise” in cancers and other illnesses for years to come, he claimed.

“The same situation will inevitably await the Ukrainian territories where they will be used,” Peskov told reporters. “The responsibility for that will lie entirely on the U.S. leadership.”

The Russian embassy located in Washington, D.C., also decried the planned uranium shipment as “an indicator of inhumanity.”

While visiting Kyiv this week, Secretary of State Antony Blinken announced the $175 million is part of a larger $1 billion funding package. The White House’s decision comes six months after the U.K. sent depleted uranium to help Ukraine’s war effort.

“In the ongoing counteroffensive, progress has accelerated in the past few weeks,” Blinken said at a Ukrainian news conference. “This new assistance will help sustain it and build further momentum.”

Next week, Russian president Vladimir Putin is expected to meet with North Korea’s Kim Jong-un to formally request military equipment, such as artillery shells and antitank missiles.