Chinese Vice President Xi Jinping is wrapping up a pivotal four-day visit to the United State with a daylong series of events in Los Angeles with his American counterpart Joe Biden, AP reported. China's soon-to-be leader met with Gov. Jerry Brown on Thursday and toured a shipping terminal at the giant Port of Los Angeles. The visit was a reminder of China's huge footprint at the busiest port in the United States. Nearly 60 percent of the imports moving through the Port of Los Angeles come from China, including $120 billion worth of computers, TVs, sneakers and other goods last year On Friday, Biden and Xi start with a China trade forum in downtown Los Angeles, followed by a luncheon and school visit to meet children learning Mandarin. They'll end the day with a governor's forum at Disney Hall. Xi's U.S. tour comes at a politically challenging time in U.S.-China relations, with the White House sending stern messages on currency and trade policies and Republican presidential candidates claiming President Barack Obama isn't doing enough to keep America competitive with the Chinese economy. The Asian power sells four times as many goods to the U.S. as the United States sends in return to China. The U.S. shipped $13.5 billion in exports to China through the Los Angeles port last year. As with his previous travels, Xi was focusing on forging relationships. China became the top market for U.S. agricultural goods last year, purchasing $20 billion in U.S. agricultural exports, according to the U.S. Department of Agriculture. Much of Xi's visit, which began earlier this week in Washington, D.C., has been focused on agriculture. The strategic cooperation agreement signed Thursday outlines mutual goals and responsibilities of each nation.