A Biden administration official recently told members of Congress that Ukraine has the military capability to retake Crimea, but some officials are concerned any large-scale offensive that threatens Russia’s hold on the peninsula could push Vladimir Putin to use nuclear weapons, say two U.S. officials familiar with the matter. The late November Ukraine briefing to some members of Congress included discussion of the reasons Ukraine will continue to need U.S. weapons and equipment for the foreseeable future. The two officials said a Biden official, when asked during the briefing about continued support for the Ukrainian military and whether it would...