South Korean engineer Kim Gwang-ho flew to Washington last year to do something he never dreamed he would: report alleged safety lapses at Hyundai Motor Co., his employer of 26 years, to U.S. regulators.

Citing an internal report from Hyundai's quality strategy team to management, Kim told the U.S. National Highway Traffic Safety Administration (NHTSA) the company was not taking enough action to address an engine fault that increased the risk of crashes.

Hyundai denies the allegations, saying in an emailed statement that it promotes openness and transparency in all safety-related operations and that its decisions on recalls comply with both global regulators and stringent internal processes.