China further isolated North Korea on Friday by closing the main road between them just a few days after the state-owned airline Air China indefinitely suspended flights from Beijing to the reclusive country.The China-North Korea Friendship Bridge is closed for “maintenance” and will be reopened once the necessary repairs are made, Foreign ministry spokesman Geng Shuang said, without offering a timeline. Meanwhile, the decision to suspend flights, announced Tuesday, was reportedly linked to a lack of demand. An official in the company’s Beijing-based press office, who refused to give a full name, simply told Reuters on Wednesday “business was not good” as he explained the decision.Correspondingly, companies in China that offer tours of North Korea have reported a sharp decline in business in recent months, blaming the drop on the “political drama.” Simon Cockerell, the general manager of Beijing-based Koryo Tours, recently told South China Morning Post he’s seen a 50 percent drop in business compared to last winter.Newsweek subscription offers >China is North Korea’s top trading partner and most important ally, but the relationship has been strained by Kim Jong Un’s erratic behavior and nuclear ambitions. In 2017, North Korea has conducted a record number of missile tests and…