South Korea has been rated the seventh-largest buyer of US defence goods, according to the Pentagon's Annual Military Assistance Report.
The country purchased $462m of weapons in 2009 through the foreign military sales (FMS) programme, the report said.
In 2009, the South Korean Navy purchased two Aegis weapons systems worth a combined $300m.
The amount is expected to increase this year due to the probability of additional naval drills being conducted by South Korea to deter provocations from North Korea.
South Korea and the US are scheduled to hold further anti-submarine drills next month, according to the Korea Times.