TOKYO (AP) — President Joe Biden has warned fellow leaders of the informal Indo-Pacific security coalition known as the Quad that they are “navigating through a dark hour in our shared history.” His warning comes as Russia continues a brutal war on Ukraine. Biden called for greater Indo-Pacific leadership in the effort to stop Russian aggression at the start of a summit Tuesday with the leaders of Australia, India and Japan. Biden did not directly call out any countries. But his message appeared to be a nudge of Indian Prime Minister Narendra Modi, with whom differences persist over how to respond to the Russia.