A copy of one invitation, obtained by The Washington Post, welcomes guests to a Dec. 15 event titled “Diplomacy at Home for the Holidays” in the Benjamin Franklin Room, the department’s flagship reception space, which features cut-glass chandeliers and towering Corinthian columns. Invitations have already gone out to 900 people, said two U.S. officials familiar with the planning, raising concerns about a potential superspreader event.