The Associated Press CAMP DAVID, Md. (AP) — President Joe Biden opened a historic summit with Japan and South Korea at Camp David on Friday focused on strengthening security and economic ties at a time of increasing concerns about North Korea’s persistent nuclear threats and China’s provocations in the Pacific. "Our countries are stronger and the world will be safer as we stand together. And I know this is a belief that all three share,” Biden declared at the start of the meeting with South Korean President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida at the presidential retreat…