Saudi Arabia was the No. 1 customer by purchasing US arms worth $13.47 billion, followed by Australia with $7.76 billion and the United Arab Emirates with $6.92 billion. Japan came in eighth with $3.64 billion.

The yearbook did not elaborate on what kinds of weapons the countries have bought from the US, though major weapons that South Korea has imported from its ally include 40 F-35A stealth fighters, four unmanned Global Hawks and various types of missiles.

Of the US' outbound shipments of weapons over the past decade, aircraft accounted for 56.1 percent, followed by missiles with 16.5 percent and armored vehicles with 11.8 percent.

During the cited period, the US imported weapons worth $7.67 billion from foreign countries, including Germany, Britain, Canada and France. South Korea was not included in the top 20.

South Korea has stressed its "reasonable and fair" level of contributions for the stationing of the 28,500-strong US Forces Korea during ongoing bilateral defense cost-sharing negotiations, though the US has been pressuring Seoul to pay more.

Washington has reportedly demanded a fivefold increase in Seoul's payments to $5 billion next year. Under this year's SMA, Seoul agreed to pay about $870 million. (Yonhap)