The White House says the controversial weapons are having an impact on Russian formations.
The White House has confirmed that Ukraine is using US cluster bombs against Russian forces in the country.
National Security Spokesman John Kirby said initial feedback suggested they were being used "effectively" on Russian defensive positions and operations.
Cluster bombs scatter multiple bomblets and are banned by more than 100 states due to their threat to civilians.
The US agreed to supply them to boost Ukrainian ammunition supplies.
Ukraine has promised the bombs will only be used to dislodge concentrations of Russian enemy soldiers.
"They are using them appropriately," Mr Kirby said. "They're using them effectively and they are actually having an impact on Russia's defensive formations and Russia's defensive manoeuvring. I think I can leave it at that."
The US decided to send cluster bombs after Ukraine warned that it was running out of ammunition during its summer counter-offensive, which has been slower and more costly than many had hoped.
President Joe Biden called the decision "very difficult", while its allies the UK, Canada, New Zealand and Spain opposed their use.
The vast majority sent are artillery shells with a lower than 2.35% "dud rate", a reference to the percentage of bomblets which do not explode immediately and can remain a threat for years.
The weapons are effective when used against troops in trenches and fortified positions, as they render large areas too dangerous to move around in until cleared.
Russia has used similar cluster bombs in Ukraine since it launched its full-scale invasion last year, including in civilian areas.
Reacting to the US decision to send the bombs, Russian President Vladimir Putin said his country had similar weapons and they would be used "if they are used against us".
Oleksandr Syrskyi, the Ukrainian general in charge of operations in the country's east, told the BBC last week that his forces needed the weapons to "inflict maximum damage on enemy infantry".
"We'd like to get very fast results, but in reality it's practically impossible. The more infantry who die here, the more their relatives back in Russia will ask their government 'why?'"
He added however that cluster bombs would not "solve all our problems".
He also acknowledged that their use was controversial, but added: "If the Russians didn't use them, perhaps conscience would not allow us to do it too."
Ukraine MOD has a program in place that databases every cluster munition fire mission. Demining eastern Ukraine is going to be a years long effort. Any unexpended ordinance will go into that effort. Countries that gave up cluster munitions have had their rose tinted glasses on too long and assumed war would be limited to foreign battlefields and not their back yards.
What's happens in Ukraine have been a topic for papers since the 1990s . It's a proxy war where two competing oligarch fractions are fighting for dominance.
As Afghanistans president said Ukraine should have learned from them. When elephants dance...
The propaganda is so total that people rather see cluster bombs than peace. Fuck that.
War is hell. That statement is both true and has lost all meaning, because no one really feels it.
We should be negotiating a peace by now. The suffering of these cluster bombs cause is immeasurable, as is the general suffering of this war.
Imagine
spoiler
beating a puppy to death with a golf club
. Imagine the whole thing vividly, and then imagine
spoiler
pushing the pulpy body aside
and doing it again, and just repeating this exercise ad nausium for hours and hours. This is the kind of feeling we should experience when we read stories about this conflict, if we had any concept of what a war is. And when we debate whether to use cluster bombs, that's like debating whether to use
spoiler
a nine iron or crush the puppy's skull slowly with a boot
. One is definitely, definitely DEFINITELY WORSE, and should NEVER BE DONE, but both are awful and should make us so physically ill to think about that we would do anything at all -- such as negotiate a ceasefire! -- to avoid doing it.
War is hell. That statement is both true and has lost all meaning, because no one really feels it.
We should be negotiating a peace by now. The suffering of these cluster bombs cause is immeasurable, as is the general suffering of this war.
Imagine ::: spoiler spoiler
beating a puppy to death with a golf club:::. Imagine the whole thing vividly, and then imagine
spoiler
pushing the pulpy body aside
and doing it again, and just repeating this exercise ad nausium for hours and hours. This is the kind of feeling we should experience when we read stories about this conflict, if we had any concept of what a war is. And when we debate whether to use cluster bombs, that's like debating whether to use
spoiler
a nine iron or crush the puppy's skull slowly with a boot
. One is definitely, definitely DEFINITELY WORSE, and should NEVER BE DONE, but both are awful and should make us so physically ill to think about that we would do anything at all -- such as negotiate an end to the war! -- to avoid doing it.