The head of the Port of Long Beach, which has been dealing with unprecedented supply chain issues in recent days, said that people who want their Christmas items on time need to shop sooner than in previous seasons. “Shop early because these delays and bottlenecks are going to continue to the end of the year,” Mario Cordero, the port’s executive director, told Bloomberg News. “Hopefully, we’ll have some strong mitigating factors.” Cordero, in the interview published Thursday, said that spiking online sales from retailers such as Amazon were, in part, causing a 24 percent year-over-year increase in containers coming into the United States in September. Both the ports of Long Beach and Los Angeles handle about 40 percent of container shipments in the United States, and they serve as key hubs for goods coming from the Asia-Pacific region into the country. Although White House press secretary Jen Psaki issued assurances …