The White House defends the move, while acknowledging that such unexploded ordnance can harm civilians.
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The US will send Ukraine a cluster munitions package to help in its counteroffensive against Russia.
The White House said it had postponed the decision for as long as it could because of the risk of civilian harm from such unexploded ordnance.
Ukraine has been asking for the weapons for months amid an ammunition shortage.
Cluster munitions – which are banned by more than 100 countries – are a class of weapons that contain multiple explosive bomblets called submunitions.
National Security Adviser Jake Sullivan told Friday’s daily White House briefing: “Ukraine has committed to post-conflict demining efforts to mitigate any potential harm to civilians and this will be necessary regardless of whether the United States provides these munitions or not because of Russia’s widespread use of cluster munitions.”
He added: “Ukraine would not be using these munitions in some foreign land. This is their country they’re defending.”
Mr Sullivan explained Ukraine was running out of artillery and needed “a bridge of supplies” while the US ramps up domestic production.
“We will not leave Ukraine defenceless at any point in this conflict period,” he said.
US officials have been hesitant to supply Ukraine with cluster munitions as they can kill indiscriminately over a wide area, threatening civilians. The US has a stockpile of these cluster bombs, which were first developed during World War II.
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The munitions are controversial because of their high failure, or dud, rates, meaning unexploded bomblets can linger on the ground for years and possibly detonate later on.
Mr Sullivan told reporters that American cluster munitions had a dud rate of below 2.5%, which he described as far below Russia’s cluster munition dud rate, which US officials say is between 30-40%.
US law prohibits the transfer of cluster munitions with bomblet failure rates higher than 1% – meaning more than 1% of the bomblets in the weapon do not explode – but President Joe Biden is able to bypass this rule.
The Pentagon noted that Russia has already been using cluster bombs in Ukraine with even higher failure rates. A United Nations investigation found Ukraine has probably used them as well, though the country has denied doing so.
Officials are planning to send artillery shells to Ukraine, with each containing 88 separate bomblets, according to US media reports. They would be fired from Howitzer artillery weapons already deployed by the Ukrainian army.
The aid package also includes Bradley and Stryker fighting vehicles, air defence missiles and anti-mine equipment, officials told reporters.
Human rights groups have urged Russia and Ukraine not to use cluster munitions and have asked the US not to supply them.
In a statement on Friday, the Office of the United Nations High Commissioner for Human Rights once again called on the countries not to use cluster bombs, arguing they were dangerous.
“Cluster munitions scatter small bomblets over a wide area, many of which fail to explode immediately,” said office spokesperson Marta Hurtado. “They can kill and maim years later. That’s why use should stop immediately.”
Some US lawmakers have also asked the Biden administration not to send the weapons, arguing their humanitarian costs outweigh their benefits in the battlefield.
Defence Department official Laura Cooper told Congress last month that military analysts had found that cluster bombs would be “useful, especially against dug-in Russian positions”.
The Biden administration’s new weapons package is worth $800m (£626.5m), CBS News reported.