The United States has classified South Korea as a second-tier country in its annual report on human trafficking for the second straight year.

In the “2023 Trafficking in Persons Report” released on Thursday, the State Department put South Korea among Tier Two countries along with Japan, Switzerland and New Zealand, citing "inadequate" efforts to prevent related crimes and protect victims.

The annual report said the country is among those that failed to fully meet the minimum standards for the elimination of trafficking, but is making significant efforts to do so.

South Korea was classified as a Tier Three country, the lowest on the scale, in the first edition of the report released in 2001 but was upgraded to Tier One the next year and maintained that classification until last year, when it was downgraded by a tier for the first time in two decades.

Meanwhile, North Korea has remained a Tier Three country on the list for the 21st consecutive year, along with 23 other countries such as China and Russia.