South Korea says it has decided to buy 40 F-35A fighter jets from Lockheed Martin for about $7 billion in the country's biggest-ever weapons purchase aimed at coping with North Korea's military threats.

South Korea agreed to the purchase of F-35A jets in March and has since been negotiating with Bethesda, Maryland-based Lockheed Martin over a price, technology transfer and other matters.

South Korea has traditionally favored importing fighter jets and other weapons from the U.S.

The state-run Defense Acquisition Program Administration says the purchase is aimed at replacing the country's aging warplanes and bolstering capability to attack strategic targets in North Korea in the event of a war.

Agency and military officials say the new jets are to be delivered to South Korea between 2018 and 2025.