Ukrainian forces are deploying cluster munitions from the U.S. appropriately, John Kirby, the National Security Councils coordinator for strategic communications at the White House, said Thursday.

The United States controversial decision to send the bombs earlier this month, which was met with widespread criticism given the threat that they pose to civilians, has been defended by Kirby and other administration officials as a necessary step.

Theyre using them effectively and they are actually having an impact on Russias defensive formations and Russias defensive maneuvering, Kirby told reporters . I think I can leave it at that.

The cluster bombs sent to Kyiv reportedly have a dud rate of less than 2.35%, meaning this percentage of bomblets wont instantly explode and could remain a threat for years to come.

Duds act like landmines and can injure civilians, wrote Mark Cancian in a recent article for the Center for Strategic and International Studies.

Russian President Vladimir Putin on Sunday warned that if cluster bombs are used against his forces, we reserve the right to mirror actions. Russia has, however, already deployed such munitions during its war with Ukraine, according to the United Nations .

U.S. Secretary of State Antony Blinken recently told MSNBC that Ukraine would have been defenseless without cluster bombs, citing a shortage of so-called unitary munitions.

The hard but necessary choice to give them the cluster munitions amounted to this: If we didnt do it, we dont do it, then they will run out of ammunition, he said. If they run out of ammunition, then they will be defenseless.

President Joe Biden had called it a very difficult decision on my part during a CNN interview on July 7.

The move was widely condemned, even by some lawmakers in Bidens own party.

Cluster bombs should never be used, Rep. Barbara Lee (D-Calif.) said on July 9. Thats crossing a line.

Defense Secretary Lloyd Austin told CNNs Wolf Blitzer last week that Ukrainians have pledged to not use the bombs to target population centers.

Ukrainians have committed in writing to make sure that these munitions are used only in the appropriate places, Austin said.

The international Convention on Cluster Munitions , which has over 100 state parties, including the United Kingdom and Germany, bans the use, production, transfer and stockpiling of cluster bombs. The U.S., Ukraine and Russia have not signed on to the treaty.