The White House warned Wednesday Russia may deploy banned weapons in its assault on Ukraine. White House Press Secretary Jen Psaki tweeted, “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.” Psaki’s comments came after the Biden administration’s mission to the United Nations amended remarks made by U.S. Ambassador Linda Thomas-Greenfield to the U.N. General Assembly last week in which she condemned Russia’s use of cluster munitions.

Linda Thomas-Greenfield: “We’ve seen videos of Russian forces moving exceptionally lethal weaponry into Ukraine, which has no place on the battlefield. That includes cluster munitions and vacuum bombs, which are banned under the Geneva Convention.”

Within hours of those remarks, the U.S. Mission to the United Nations edited Ambassador Thomas-Greenfield’s transcript, changing her comments to read that the weapons have no place on the battlefield if they are directed against civilians. The United States fought against the creation of the Convention on Cluster Munitions and is not among the 110 nations that have ratified the treaty.

The U.S. has repeatedly used cluster bombs throughout its history, dropping them over Vietnam, Laos, Cambodia, Iraq and elsewhere. Under President Barack Obama in 2009, a U.S. cluster bomb attack in Yemen killed 55 people, the majority of them women and children. Russia and Ukraine also have not signed on to the Convention on Cluster Munitions.