Washington has sent a “letter of acceptance” for Seoul’s project to buy Global Hawk spy drones following congressional approval for the sale, Seoul officials said Thursday.

“The LOA has been delivered to us for the sale of Global Hawks and we are going over it now,” an official at the Defense Acquisition Program Administration said, declining to be named.

Seoul made the purchase request to the U.S. in December 2005 and the congressional approval had been delayed for the sale of the high-flying, long-endurance military aircraft.

Seoul initially sought to deploy four of the unmanned aerial vehicles by 2015 with a budget of 450 billion won ($408 million). The challenge facing the procurement project is the price, which jumped over time.

“The estimated price for the project has exceeded our budget by more than 20 percent,” the official said.

South Korea has been seeking to bolster its intelligence, reconnaissance and surveillance assets as part of preparations to retake wartime operational control slated for December 2015.

Seoul is now considering whether to bring in other competitors such as AeroVironment’s Global Observer and Boeing’s Phantom Eye for the high-stakes project.

The single-engine Global Hawk can fly at an altitude of 18 kilometers or higher for 36 hours. With an operational range of 3,000 kilometers, it is capable of covering not only all of North Korea but also parts of China and other neighboring countries.

By Song Sang-ho(sshluck@heraldcorp.com)