South Korea should not cross off F-15 fighter jets from its shopping list aimed at boosting combat capability, a former top U.S. military commander in Korea said Tuesday.

"In a real sense, a mix of F-35s and F-15s is the right decision," retired Gen. John Tilelli told reporters.

His comments came amid media reports that South Korea will likely announce plans to buy 40 F-35s in the coming weeks.

Tilelli, who headed U.S. Forces Korea (USFK) from 1996 to 1999, emphasized that carrying weight is as important as stealth to counter North Korea's threats.

Keen attention is being paid to South Korea's choice in the US$7.4-billion project.

Seoul initially came close to selecting Boeing's F-15SE as Lockheed Martin's F-35 and the Eurofighter Typhoon were priced too high.

But South Korea has re-opened the bidding, bowing to a strong backlash from a group of retired Air Force officials demanding the purchase of an F-35.

The retired general, who now works at a defense consulting firm, emphasized that South Korea needs F-15s as part of "bridge capability" before achieving its longer-term goal of having enough ability to play a leading role, with the U.S. playing a supporting role, in a war against North Korea.

He expressed skepticism over South Korea's push for an independent missile defense system, dubbed "Korea Air and Missile Defense."

He called for the U.S.-led integrated missile defense networks, adding, "It should not be a stand-alone system" sought by Seoul.

On the timing of transferring the operational control (OPCON), he voiced opposition to setting a specific timeline.

"OPCON transfer must be based on condition rather than time. So we have to look at the conditions on the peninsula at large, the threat and the capabilities, and then determine when OPCON transfer is appropriate," he said in a round table hosted by the Center for a New American Security (CNAS), a Washington-based think tank.

South Korea is scheduled to regain wartime OPCON of its troops in 2015. The Park Geun-hye administration, however, has requested a further delay in the OPCON transition, citing North Korea's growing nuclear and missile threats.

"Realistically, the U.S. must take that request very seriously," Tilelli said.

He especially took issue with a plan to dissolve the South Korea-U.S. Combined Forces Command after the OPCON transition, saying it is one of the best alliance mechanisms in existence.

"In my view, the Combined Forces Command should remain exactly the way it is today, and as we look to the future, determine what is the necessity of changing the command structure at all," he said.

Just as his predecessors and successors, Tilelli wore two other hats -- the commander of the United Nations Command (UNC) and the South Korea-U.S. Combined Forces Command (CFC).

He said the CFC is effective not only in terms of military strategy and operation but also in promoting people-to-people exchanges between the troops and the families of the allies. (Yonhap News)