President Joe Biden secretly gave Ukraine permission to use U.S. weapons to strike inside Russia, two American officials said Thursday. The decision is a U-turn that Kyiv’s allies hope helps turn the tide of the war.

The decision, which applies only to the area around the northeastern city of Kharkiv, aims to ensure that Ukrainian forces can strike the Russian military as it attacks or prepares to attack, said the officials, who spoke on condition of anonymity. Long-range strikes inside…