Russia's Defense Minister threatened use of weapons similar to cluster bombs if the U.S. supplied them to Ukraine.
The U.S. announced last week it would supply Ukraine with cluster munitions – explosive weapons that typically release large numbers of smaller bomblets over a wide area. They are banned by over 100 countries, including Britain and Japan.
Shoigu was quoted as saying that Russia was in possession of cluster munitions but had so far refrained from using them in its military campaign.
However, the U.S. has previously accused Russia of using cluster munitions in Ukraine and said they have had a failure rate of up to 40%, leaving the ground littered with unexploded bomblets. Washington says the cluster munitions it is sending to Ukraine have a failure rate of less than 2.35%.
"In the event that the United States supplies cluster munitions to Ukraine, the Russian armed forces will be forced to use similar weapons against the armed forces of Ukraine as a response," Shoigu said on Tuesday.
"It should be noted that Russia has cluster munitions in service... for all occasions... They are much more effective than American ones...," he said.
Shoigu added that the Russian army was taking measures to protect its troops from such weapons.
Human Rights Watch says both Moscow and Kyiv have used cluster munitions during the nearly 17-month conflict in Ukraine, which Russia calls a "special military operation".
The U.S. Russia and Ukraine have not signed up to the Convention on Cluster Munitions.
U.S. officials say they granted Kyiv's request for cluster bombs after it became apparent that Ukraine – now waging a counteroffensive against Russia – was running out of regular artillery ammunition and production would not meet its needs.
Close U.S. allies including Britain, Canada and Germany have expressed their opposition to the use of cluster munitions.
In other comments, Shoigu said Russia was "significantly reducing" the potential of Ukraine's counteroffensive and that Russian forces had gained ground during their own counterattack in the direction of Lyman in Ukraine's eastern Donetsk region.
Donald Trump on Tuesday criticized the Biden administration's decision to send cluster munitions to Ukraine.
"Joe Biden should not be dragging us further toward World War III by sending cluster munitions to Ukraine – he should be trying to END the war and stop the horrific death and destruction being caused by an incompetent administration," the former U.S. president wrote on his official website.
Trump said unexploded munitions will be killing, maiming innocent Ukrainians for decades.
"If, as Biden inadvertently admitted, the reason for sending cluster bombs now is that the United States is ‘running out of ammunition (a great breach of classified information), that only further emphasizes the urgency of immediately de-escalating this bloody, dangerous, and out of control conflict," he said,
It means the U.S. should not be sending Ukraine its last stockpiles at a time when its own arsenals are diminished, said Trump.
He added: "Joe Biden's policy of endless war in Ukraine" has weakened the U.S., which is something U.S.' enemies are "salivating over."
He urged Biden to stop this immediately and end the bloodshed in Ukraine and return to America's most vital interests.
The U.S. should completely rebuild its depleted military so that no nation would think of threatening the American people, he said.
"We must have ‘PEACE THROUGH STRENGTH' and in a short time, the Presidential election of 2024 will produce that result," he said.
Biden said last week he decided to provide Ukraine with cluster bombs because Kyiv is running out of 155 mm artillery.
