ZURICH/WASHINGTON—The United States and China have agreed in principle for their presidents to hold a virtual meeting before the end of the year, a senior U.S. administration official said on Wednesday, after high-level talks aimed at improving communication between the two countries. The closed-door meeting at an airport hotel in the Swiss city of Zurich between U.S. national security adviser Jake Sullivan and China’s top diplomat Yang Jiechi was their first face-to-face encounter since an unusually public and acrid airing of grievances in Alaska in March. U.S. officials had suggested that the meeting was a follow-on from President Joe Biden’s Sept. 9 call with Chinese President Xi Jinping, prior to which the world’s top two economies appeared to have been locked in a stalemate. The White House said Sullivan raised concerns about contentious issues such as China’s actions in the South China Sea, as well as on human rights and …