The White House has denied that the United States has biological weapon laboratories or is developing chemical weapons in Ukraine.

White House press secretary Jen Psaki expressed concern that Russia’s allegations to the contrary have been amplified by China, pointing to the possibility for Russia to launch such an attack against Ukraine as its forces encounter unexpected challenges during the two-week war.

“This is all an obvious ploy by Russia to try to try to justify its further premeditated, unprovoked, and unjustified attack on Ukraine,” Psaki said Wednesday.

“Now that Russia has made these false claims, and China has seemingly endorsed this propaganda, we should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine or to create a false flag operation using them,” she added. “It’s a clear pattern.”

Psaki ripped Russia’s “conspiracy theories” as “preposterous.” Instead, she remained adamant that the Biden administration is in full compliance with its Chemical Weapons Convention and Biological Weapons Convention obligations and “does not develop or possess such weapons anywhere.”

“It’s Russia that has a long and well-documented track record of using chemical weapons, including in attempted assassinations and poisoning of Putin’s political enemies like Alexey Navalny,” she said. “It’s Russia that continues to support the Assad regime in Syria, which has repeatedly used chemical weapons. It’s Russia that has long maintained a biological weapons program in violation of international law.”

Undersecretary of State for Political Affairs Victoria Nuland told the Senate Foreign Relations Committee this week that the U.S. is worried Russia wants control of Ukrainian biological or chemical research facilities.

“We are working with the Ukrainians on how they can prevent any of those research materials from falling into the hands of Russian forces should they approach,” she said.

Russia has so far captured the Zaporizhzhia Nuclear Power Plant in Enerhodar, Ukraine, and the infamous Chernobyl Nuclear Power Plant north of Kyiv.