For more than six months, U.S. President Joe Biden and his aides have been wrestling with one of the most vexing questions in the war in Ukraine: whether to risk letting Ukrainian forces run out of the artillery rounds they desperately need to fight Russia, or agree to ship them cluster munitions — widely banned weapons known to cause grievous injury to civilians, especially children.

On Thursday, Biden appeared on the verge of providing the cluster munitions to Ukraine, a step that would sharply separate him from many of his closest allies, who have signed an international treaty banning the use, stockpiling or transfer of such weapons.

Several of Biden’s top aides, including Secretary of State Antony Blinken, recommended he make the move at a meeting of top national security officials last week, despite what they have described as their own deep reservations, people familiar with the discussions said. They requested anonymity to discuss sensitive deliberations.