HONG KONG/NEW YORK—Persistent default fears eclipsed efforts by China Evergrande Group’s chairman to lift confidence in the embattled firm on Tuesday, as Beijing showed no signs it would intervene to stem any domino effects across the global economy. Analysts played down the threat of Evergrande’s troubles becoming the country’s “Lehman moment,” though concerns about the spillover risks of a messy collapse of what was once China’s top-selling property developer have roiled markets. In an effort to revive battered confidence in the firm, Evergrande Chairman Hui Ka Yuan said in a letter to staff the company is confident it will “walk out of its darkest moment” and deliver property projects as pledged. In the letter, coinciding with China’s mid-autumn festival, the chairman of the debt-laden property developer, also said Evergrande will fulfil responsibilities to property buyers, investors, partners, and financial institutions. “I firmly believe that with your concerted effort and hard …