Negotiations to end a drawn-out rail walkout broke down Friday, with the state-run rail operator issuing an ultimatum for thousands of strikers to get back to work by midnight or face punitive measures. Labor and management of the state-run Korea Railroad Corp. (KORAIL) gathered at the negotiating table earlier in the day after resuming the second round of their working-level negotiations to discuss key issues, including a government plan to establish a subsidiary to run some high-speed train services