(NewsNation) — The United States has denied Russian accusations that Washington was operating biowarfare labs in Ukraine and suggested Moscow may be laying the groundwork to use a chemical or biological weapon.

The repeated Russian accusation, which has spanned several years, claims the United States is working with Ukrainian laboratories to develop biological weapons.

Andy Weber, a senior fellow at the Council on Strategic Risk — who has seen the labs in Ukraine firsthand — said there is nothing nefarious happening in them.

“They function just like your county public health laboratory,” Weber said. “They monitor for infectious disease outbreaks … they’re sort of a smaller version of the Centers for Disease Control. I’ve visited them many, many, many times, as have international visitors and the World Health Organization routinely.”

In addition, the United States has been working with them since 2005 to find better systems of detecting and responding to infectious disease outbreaks. And the United States hasn’t just partnered with Ukraine.

“It’s part of a global early warning system for infectious disease outbreaks,” Weber said. “Just as we fight terrorism abroad because we don’t want the attacks to occur in the United States, we want to stop infectious disease outbreaks at the source wherever they may occur.”

Ukraine’s laboratories have received support from the United States, European Union and World Health Organization.

The State Department said Russia “is inventing false pretexts in an attempt to justify its own horrific actions in Ukraine.”

A former U.S. official, who is familiar with the cooperation between Kyiv and Washington, told Reuters the United States had helped to convert several Ukrainian laboratories that had been involved in the former Soviet Union’s biological weapons program into public health facilities.

Reuters contributed to this report.