Secretary of State Antony Blinken speaks during the 2022 Trafficking in Persons (TIP) Report launch ceremony at the State Department in Washington, U.S., July 19. Reuters-Yonhap

The U.S. State Department on Tuesday downgraded South Korea in its annual human trafficking report by a tier for the first time in two decades, citing insufficient efforts in tackling related crimes and protecting victims.

South Korea was placed on Tier 2 in the 2022 Trafficking in Persons Report, down from the highest classification of Tier 1 the country had maintained since 2002, along with 132 other nations, including Japan, Norway and Switzerland.

The document classifies 188 nations into four tiers ― Tier 1, Tier 2, Tier 2 "watchlist" and Tier 3 ― in terms of actions in preventing trafficking, protecting victims and prosecuting traffickers.

"The government initiated fewer prosecutions than in 2020, did not take steps to address longstanding concerns that government officials penalized foreign sex trafficking victims for unlawful acts traffickers compelled them to commit, and sometimes deported victims without providing them adequate services or investigating traffickers," the report read.