South Korea formally opened bidding Tuesday on a $7.3 billion deal to provide 60 advanced fighter planes, with three aviation giants vying for what is the Asian nation's largest defence contract to date.

US companies Boeing and Lockheed Martin and the European aerospace consortium EADS are in the running, and all have prefaced their bids with various sweeteners to try and edge out their rivals.

South Korea's Defence Acquisition Program Administration (DAPA), which will assess the bids, has made it clear that it cannot exceed the 8.3 trillion won ($7.3 billion) budget approved by parliament.

The choice will be between Boeing's F-15 Silent Eagle, Lockheed Martin's F-35 Lightning II and the EADS Eurofighter Typhoon.

EADS has offered a $2.0 billion investment in a separate South Korean project to develop its own advanced fighter jets, if the consortium is chosen.

Lockheed Martin offered to support South Korea's effort to develop and launch military communications satellites, while Boeing promised to buy billions of dollars in parts from Korean companies.

The bidding process is scheduled to last 11 days.

South Korea's military procurement needs, especially where the air force is concerned, have overwhelmingly been met by US suppliers in the past -- a reflection of their close military alliance.

But EADS' hopes were raised in January, when the Anglo-Italian company AgustaWestland beat out US defence giant Sikorsky for a $567 million contract to supply six helicopters to the South Korean navy.