UNITED NATIONS (AP) — The United States accused Russia of using a U.N. Security Council meeting Friday for “lying and spreading disinformation” as part of a potential false-flag operation by Moscow for the use of chemical or biological agents in Ukraine.

U.S. Ambassador Linda Thomas-Greenfield said Russia was playing out a scenario put forth in the council last month by U.S. Secretary of State Antony Blinken — that President Vladimir Putin would “fabricate allegations about chemical or biological weapons to justify its own violent attacks against the Ukrainian people.”

“The intent behind these lies seems clear, and is deeply troubling,” she said. “We believe Russia could use chemical or biological agents for assassinations, as part of a staged or false-flag incident, or to support tactical military operations.”

Russia had requested the council meeting to address its allegations of U.S. “biological activities” in Ukraine — a charge made without any evidence and denied by both Washington and Kyiv.

Britain’s U.N. Ambassador Barbara Woodward, called the allegations “utter nonsense” and said “Russia is sinking to new depths today, but the council must not get dragged down with it.”

U.N. disarmament chief Izumi Nakamitsu told the council she was aware of media reports about allegations of biological weapons programs and said: “The United Nations is not aware of any biological weapons programs.”

Thomas-Greenfield said Ukraine doesn’t have a biological weapons program or biological weapons laboratories supported by the United States, as Russia claimed. Ukraine does own and operate its own public health laboratory facilities that make it possible to detect and diagnose diseases like COVID-19, which the U.S. has assisted Ukraine in doing “safely and securely.”

Thomas-Greenfield said that ever since Russia began building up forces near Ukraine’s borders, Washington’s strategy has been to counter Moscow’ tactics and share what it knows with the world.

“We’re not going to let Russia get away with lying to the world or staining the integrity of the Security Council by using it as a venue for legitimizing Putin’s violence,” she said.

“We do not sit in this chamber to be an audience for Russia’s domestic propaganda,” Thomas-Greenfield added. “And we should not allow Russia to abuse its permanent seat to spread disinformation and lies and pervert the purpose of the Security Council.”

The U.N. human rights office has received “credible reports” that Russian forces are using cluster munitions in Ukraine, including in populated areas, which is prohibited under international humanitarian law, Undersecretary-General Rosemary DiCarlo told the Security Council.

“Indiscriminate attacks, including those using cluster munitions, which are of a nature to strike military objectives and civilians or civilian objects without distinction, are prohibited under international humanitarian law,” DiCarlo said. “Directing attacks against civilian and civilian objects, as well as so-called area bombardment in towns and villages, are also prohibited under international law and may amount to war crimes.”

Russia’s U.N. Ambassador Vassily Nebenzia replied that the allegations are “refuted repeatedly by our Ministry of Defense.”

The Russian request for the Security Council meeting, tweeted Thursday by its first deputy U.N. ambassador, Dmitry Polyansky, followed a U.S. rejection of Russian accusations that Ukraine is operating chemical and biological labs with U.S. support.

Russian Foreign Ministry spokeswoman Maria Zakharova had made the accusation earlier this week, following a warning from White House press secretary Jen Psaki that Russia might use chemical or biological weapons against Ukraine in the invasion.

Psaki called Russia’s claim “preposterous” and tweeted: “This is all an obvious ploy by Russia to try to justify its further premeditated, unprovoked, and unjustified attack on Ukraine.”

Ukrainian President Volodymyr Zelenskyy also denied Russia’s accusation. Like Psaki, he said the accusation itself was a bad sign.

“That worries me very much because we have often been convinced that if you want to know Russia’s plans, they are what Russia accuses others of,” he said late Thursday. “No chemical or any other weapon of mass destruction has been developed on my land. The whole world knows this.”

Pentagon press secretary John Kirby called the Russian claim “a bunch of malarkey.”

Olivia Dalton, spokesperson for the U.S. Mission to the United Nations, said “Russia has a well-documented history of using chemical weapons and has long maintained a biological weapons program in violation of international law” as well as “a track record of falsely accusing the West of the very violations that Russia itself is perpetrating.”

U.N. disarmament chief Izumi Nakamitsu and U.N. political chief Rosemary DiCarlo also were scheduled to brief the council Friday.

U.N. spokesman Stéphane Dujarric reiterated Thursday that the World Health Organization, which has been working with the Ukrainian government, “said they are unaware of any activity on the part of the Ukrainian government which is inconsistent with its international treaty obligations, including on chemical weapons or biological weapons.”

The United States for months has warned about Russian “false flag” operations to create a pretext for the invasion, which began Feb. 24.

The White House warning, and Dalton’s statement Thursday, suggested Russia might seek to create a pretense for further escalating the two-week-old conflict that has seen the Russian offensive slowed, but not stopped, by stronger-than-expected Ukrainian defenders.

The international community for years has assessed that Russia used chemical weapons in carrying out assassination attempts against President Vladimir Putin’s opponents such as Alexei Navalny, now in a Russian prison, and former spy Sergei Skripal, who lives in the United Kingdom. Russia also supports the Syrian government, which has used chemical weapons against its people in an 11-year civil war.