ROME (AP) - President Joe Biden is convening world leaders at the Group of 20 summit on Sunday to talk about ways to relieve the supply chain bottlenecks hampering the global economy as it recovers from the coronavirus pandemic.Despite devoting a combined $15 trillion to combat the fallout from COVID-19, many of the world's largest economies are slogging through mass shortages as ships are waiting to dock, the prices of shipping containers climb, not enough trucks exist to haul goods from ports, and virus outbreaks halt factory production.Supply chain issues have emerged as a point of economic and political pain for Biden, as the delays have contributed to inflation and potentially put a damper on holiday shopping.