SEOUL, Sept. 23 (Yonhap) -- South Korea is pushing for the development of its own version of advanced Patriot missiles to counter North Korean ballistic missiles, military sources said Friday.

Multiple sources said the state-run Defense Agency for Technology and Quality (DATQ) will complete by the end of this year its preliminary research on long-range surface-to-air missiles (L-SAMs), which could intercept North Korean ballistic missiles or fighter jets at high altitudes.

According to the sources, the military will finalize the basic outline for further development around January or February next year, and the exploratory development will get underway in 2013.

They said the development cost for about 10 such missiles could reach 970 billion won ($813 million).

The sources said the South Korean L-SAMs will try to attain a range of up to 60 kilometers, which is more than double the range of the U.S. Patriot Advanced Capability-3 (PAC-3) missile currently in use, and four times that of PAC-2 missiles and the Iron Hawk-II surface-to-air guided missiles used by the South Korean forces.

Sources also said the new L-SAMs will be more accurate than existing interceptors.

"The development of L-SAMs was first included in the early planning for the defense reform in 2009, and the cost was determined in April last year," one source said. "They will be deployed to protect key national facilities and military bases in the central and southern regions."