The United States has decided to remove Thailand from its list of worst human trafficking offenders, officials said, a move that could help smooth relations with Bangkok's military-run government.

The upgrade, confirmed by a U.S. official in Washington and a Bangkok-based official from an international organization with direct knowledge of the rankings, will mark a rare boost for U.S.-Thai relations. Ties between the countries have flat-lined since the Thai military seized power in a 2014 coup that Washington strongly condemned.

It also comes as U.S. President Barack Obama works to forge a united front among wavering Southeast Asian countries against China's pursuit of its territorial claims in the South China Sea.