South Korea is poised to buy four Global Hawks from Northrop Grumman through the U.S. Foreign Military Sale (FMS) program, with a decision expected to come early next year, a government source said Friday.

Seeking better surveillance capabilities on North Korea, Seoul has sought to buy the high-altitude, long-endurance unmanned aerial vehicles (UAVs), obtaining sales approval for four airplanes from the U.S. government in April.

But the higher-than-expected cost for four RQ-4 Block 30s, which was valued at $1.2 billion by the Pentagon, caused Seoul to reconsider its plan for a government-to-government program and hold an open competition with other potential deals on the table, including Boeing's Phantom Eye and AeroVironment Inc.'s Global Observer.

As the two other candidates fell short of the military requirements, the Defense Acquisition Program Administration (DAPA) picked the Global Hawk as the only candidate and recently requested the U.S. government to grant letters of acceptance (LOA) for the spy drones.

"The (DAPA) decided to buy Global Hawks through the government-to-government FMS program," a senior DAPA official said, asking for anonymity as the decision was not formalized. "Once the U.S. sends LOA (to DAPA) within this year, we will make a formal decision on the purchase of the Global Hawks."

The decision comes after the Korea Institute for Defense Analyses has re-evaluated the estimated budget, and the finance ministry approved an extension of funding for the program, according to officials.

If the acquisition plan is approved, the South Korean military is expected to deploy four drones in 2017, according to officials. 

Global Hawks operate at considerable stand-off distances and in any weather or light conditions, and can carry up to 1,360 kilograms of an internal payload. Associated with command and control base stations, the system's advanced radar will continuously detect and track moving objects throughout observed areas on the Korean Peninsula.

Northrop officials have promised industrial cooperation and technology transfer to facilitate sales of Global Hawks, highlighting their critical role in monitoring North Korea to take an early action in time of conflict.

As part of marketing efforts, the Virginia-based defense company displayed the full-size mock-up aircraft during the Seoul International Aerospace and Defense Exhibition (ADEX), which opened on Tuesday and runs through Sunday. (Yonhap News)