"We are firmly against the use of cluster bombs everywhere and anywhere. They are a horrifying tool of war," Dujarric said during a press conference.
The United Nations wants to see an end to the conflict in Ukraine and hopes to see the territorial integrity of the country preserved.
On July 7, the US government unveiled a new military aid package for Ukraine that included cluster munitions. The move was widely criticized in many quarters, including allies in the European Union as well some US lawmakers.
On Thursday, Defense Department spokesperson Pat Ryder said that the information provided by the Ukrainians to the United States indicates Kiev is using the cluster munitions appropriately.
The Convention on Cluster Munitions, which bans their use, has been ratified by 123 countries. The United States, Ukraine, Russia, China, India, Pakistan, Israel and South Korea have not signed the convention.