The United States on Tuesday listed China as among the worst countries for human trafficking while Japan remained in Tier 2, the second-highest classification on the four-tier list.

In the 2017 Trafficking in Persons Report, the State Department dropped China from the Tier 2 Watch List to Tier 3, putting it on a par with nations including Russia, North Korea, Syria and Iran.

China's downgrading is expected to upset the leadership in Beijing, with President Donald Trump's administration having so far refrained from taking actions that could provoke what it sees as a key partner in reining in North Korea's nuclear arms and missile programs.