The United States on Thursday warned that instability sparked by the global coronavirus pandemic has opened the door to increased human trafficking.
Washington also added Afghanistan, Algeria, Lesotho and Nicaragua to its blacklist on human trafficking in its annual report on the illegal practice.
"While urgency has always marked the fight against human trafficking, the implications of the COVID-19 pandemic have magnified the need for all stakeholders to work together in the fight more than ever," Pompeo said in the report's introduction.
"We know that human traffickers prey upon the most vulnerable and look for opportunities to exploit them," he said.
"Instability and lack of access to critical services caused by the pandemic mean that the?number of people vulnerable to exploitation by traffickers is rapidly growing."
The US ambassador-at-large on human trafficking, John Richmond, hammered home the point: "Traffickers did not shut down. They continue to harm people, finding ways to innovate and even capitalize on the chaos."
Countries on the US trafficking blacklist are seen as not doing enough to combat the scourge.
Such a designation can lead to sanctions: the United States can opt to either limit aid or withdraw its support for the countries within international institutions like the International Monetary Fund.
The four nations added to the list of worst offenders join 15 others already there, including China, Iran, North Korea, Russia, Syria and Venezuela.
US ally Saudi Arabia was removed from the blacklist, after being designated last year. Mauritania also was upgraded -- both are now on the so-called Tier 2 watch list.
In a rare move, Ireland was put on the Tier 2 watch list, as was Hong Kong.
The US said Ireland "has not obtained a trafficking conviction" since amending its laws in 2013 in a way that "weakened deterrence, contributed to impunity for traffickers, and undermined efforts to support victims to testify."
As for Hong Kong, the State Department said it was downgraded as the city's government "did not enact legislation to fully criminalize all forms of trafficking."
In an annual US report on human trafficking, Secretary of State Mike Pompeo says instability created by the coronavirus pandemic is making more people vulnerable to traffickers