President Biden said the United States will not send F-16 fighter jets to Ukraine, rejecting renewed calls by Kyiv officials for these advanced weapons to turn the tide of the conflict and boost Ukraine’s command of its own airspace. Buoyed by long-sought commitments last week from the United States and Germany to send tanks, a Ukrainian official described fighter jets as Kyiv’s “next big hurdle.” But other allies also voiced reluctance to send them.