The never-ending supply of weapons to Ukraine is advancing once again. Now the Pentagon claims Kyiv could use some cluster bombs.

United States-supplied cluster munitions would be “useful” to Ukraine, claiming they would be effective against Russian fortifications as Kyiv presses ahead with its counter-offensive. “Our military analysts have confirmed that DPICMs would be useful, especially against dug-in Russian positions on the battlefield,” Cooper said, referring to the cluster weapons by their formal name, Dual-Purpose Improved Conventional Munitions.

According to a report by RT, she added that the White House has been unable to meet Kyiv’s repeated requests for the bombs due to “existing congressional restrictions” and “concerns about allied unity.”

Cluster bombs carry smaller explosive submunitions which are released in flight and scattered across a target area, typically used against personnel and lightly armored vehicles. However, due to their tendency to leave behind undetonated ‘duds’ – which can remain live in former conflict zones for decades – more than 120 nations have agreed to ban the weapon, including most NATO members. –RT

While Washington has not joined the International Convention on Cluster Munitions, Congress passed a law in 2009 that prohibited the exports of any cluster bombs with a “dud” rate of more than 1%, which applies to most of the U.S.’s stockpile. Though the measure effectively bans all foreign transfers of the weapon, President Joe Biden can waive the restriction at any time.

Several Republican lawmakers have urged the White House to do just that, with a group of GOP congressmen and senators telling Biden in March to ignore “vague concerns about the reaction of allies and partners and unfounded fears of ‘escalation.’” Democrats have been less vocal about the issue, but some prominent party members have said the weapons should not be ruled out.

Moscow has repeatedly warned that the supply of foreign arms to Kyiv will only prolong the conflict while doing little to deter its military objectives. Responding to earlier calls for cluster munitions, Deputy Foreign Minister Sergey Ryabkov said the move would mark a major escalation by Washington and only serve to undermine the security of the NATO bloc.

So far, Russia has not retaliated against countries that supply Ukraine with weapons.