TOKYO—U.S. Secretary of State Antony Blinken warned China on Tuesday against using “coercion and aggression” as he sought to use his first trip abroad to shore up Asian alliances in the face of growing assertiveness by Beijing. China’s extensive territorial claims in the East and South China Seas have become a priority issue in an increasingly testy Sino-U.S. relationship and are an important security concern for Japan. “We will push back, if necessary, when China uses coercion and aggression to get its way,” Blinken said. His visit to Tokyo with Defense Secretary Lloyd Austin is the first overseas visit by top members of President Joe Biden’s cabinet. It follows last week’s summit of the leaders of the Quad grouping of the United States, Japan, Australia and India. Blinken’s comments come ahead of meetings in Alaska on Thursday that will bring together for the first time senior Biden administration officials and …