Nicolas Gonzalez equalised for Argentina four minutes before half-time when he bulleted a header home from a Giovani Lo Celso corner kick.
A stoppage-time goal by substitute Haris Seferovic gave Switzerland a 2-1 World Cup Group E win over Ecuador on Sunday.
World No 1 Novak Djokovic maintained his perfect tournament record and advanced to his fifth China Open final with a 6-3, 6-4 victory against Andy Murray on Saturday.