Two arms procurement officials said the bidding began Tuesday and is scheduled to end next week. Boeing's F-15 Silent Eagle, EADS' Eurofighter Typhoon and Lockheed Martin's F-35 Joint Strike Fighter are competing.
The deal would be South Korea's biggest arms purchase ever. The 60 fighter jets will replace the country's aging fleet of F-4s and F-5s.
Both officials at the Seoul-based Defense Acquisition Program Administration declined to be identified by name, citing office policy.
South Korea faces rival North Korea over a heavily armed border. The 1950-53 Korean War ended in a truce that has left the Korean Peninsula technically at war.