Washington - The United States released its annual human trafficking report on Thursday and added eight countries, including Uzbekistan and fledgling democracy Myanmar, to the blacklist of those not doing enough to halt it.
Djibouti, Haiti, Papua New Guinea, Sudan, Suriname and Turkmenistan were also added to the now 26-strong blacklist of governments the State Department believes are not fighting people smuggling or slavery.
Kuwait and Thailand found themselves promoted from this "Tier 3" list of worst offender to the "Tier 2 watch list" of countries making some kind of effort to combat the trade in persons but still under scrutiny.
Libya, Somalia and Yemen were judged special cases whose governments are in too much chaos to be judged.
"This is a heck of a piece of work," US Secretary of State John Kerry said, introducing the report, which is mandated by the US Congress to monitor progress around the world in the fight against exploitation.
"There are some tough calls," he admitted, but insisted that the list was based on facts and set criteria, not political considerations - a criticism of past reports.
Last year, the State Department was criticised for not including Myanmar on its Tier 3 list, amid allegations that Washington was turning a blind eye to slavery in order to encourage a slow transition to democracy.
This year's report on Myanmar dubs it "a source country for men, women, and children subjected to forced labour and for women and children subjected to sex trafficking, both in Burma and abroad".
Washington has also been accused of taking too lenient an approach to Uzbekistan, where the government makes no attempt to hide the fact that it press-gangs civil servants into forced labour to harvest cotton.
Human rights watchdogs welcomed the demotion of Myanmar and Uzbekistan, which they felt had been unfairly protected from scrutiny for political reasons in last year's report, but expressed regret that Thailand and Malaysia were not being held to account.
"We're encouraged by the State Department's decision to downgrade Burma -- that was a country that we were paying pretty close attention to," said Kristen Abram, acting director of anti-trafficking umbrella group Atest.
"We're also equally encouraged by the right of last year's wrong on Uzbekistan, a country that has state orchestrated forced labour," she said.
But watchdogs remain concerned that Washington is going easy on its allies in Southeast Asia, where the fishing industry in particular is regularly accused of using forced labour in inhumane conditions at sea.
"Starting with Thailand, we have seen some willingness to reform some of their laws, but it's not made any significant impact on the ground," Abrams said.
"With Malaysia, we know that they were moved up last year for political reasons. It was unjustified then and it remains unjustified today," she said, citing a failure to investigate a mass grave of alleged forced workers.