U.S. Secretary of State John Kerry says Malaysia was upgraded from the lowest ranking in a U.S. human trafficking report because it made significant improvements, not to ensure its continued participation in talks for a U.S.-backed regional trade pact.

Malaysia was upgraded last month from the "Tier 3" ranking it received in last year's State Department report on trafficking. Critics contend that the decision was related to its participation in negotiations for a Trans-Pacific Partnership Agreement that Washington is eager to conclude.

Kerry said Thursday he signed off on the trafficking report and had no conversations with anyone about links between it and the TPP talks.

Despite the upgrade, Kerry said Malaysia still has "a long way to go" and would be demoted if it fails to follow through.