Leaders of Australia, India, Japan and the United States expanded joint security steps in Asia's trade-rich waters as outgoing U.S. President Joe Biden hosted counterparts from the Quad grouping established due to shared concerns about China.

"It will survive way beyond November," Mr. Biden declared of the Quad as the leaders gathered at the Archmere Academy, his high school alma mater.

The president warned leaders of Japan, India and Australia that Beijing "continues to act aggressively" during his hometown summit.