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."
I don't have the energy for fights. Just look at some of the other comments I posted. The TLDR is that we need to always be guided by actually acting in the interests of vulnerable Ukrainians, and that requires ending the war, and negotiation is how wars end. It's not surrender, it's not appeasement, it's how wars end even when you win. What's happening now is mostly driven by US interests to weaken a geopolitical foe and is totally divorced from concern for the people on the ground. Cluster bombs prove it.
I don't think you or me or anyone in this thread would ever, ever support the use of cluster bombs in a place where we intended to raise our children or children's children. Does that make sense? Their use is just evidence that hurting Russia is the point. Negotiation is how you do the actual thing people seem to believe fighting does.
Russians are more dangerous than land mines. Even if you had to make that area impossible to live in, it is still better than having russians there.
*russian troops
Coscripts = russians. I stand by what I wrote.
Genocidal rhetoric.
Vast majority of russians support putin. So yeah, I stand by my words.
Genocide = killing whole or parts of a nation.
Saying russians could gtfo ukraine is not genocidal. No, genocidal is what the russian vermin is doing in ukraine.
Do you hear yourself? You're honestly defending making an area uninhabitable?
This is madness. This is the kind of blind jigoism that leads people to believe that it would be better to slag the planet if it meant that the adversary died too. This isn't a god damn movie, people. You're talking about other people's homes.
East ukraina = \ = whole planet. Yor logic is faulty.
Besides, it is much easier to remove unexploded cluster munition than russian vermin.
What is there to negotiate? Russia can leave Ukraine and the war is over. It really is that simple. Why are you advocating for some sort of negotiation?
Someone moves into your house, kills half your family, then holds up in your living room for half a year. Should you negotiate with them on the basis that they keep your living room now?