U.S. Secretary of State John Kerry on Friday labeled the North Korean government led by Kim Jong Un an "illegal and illegitimate regime" — unusually strong language from America's top diplomat.

Speaking after a meeting with Kuwaiti Foreign Minister Sabah al-Khalid al-Sabah, Kerry praised the Persian Gulf nation's moves to counter the North's nuclear proliferation activities, saying it had "recently taken steps to curb flights and to make sure that revenues from workers are not sustaining any illegal and illegitimate regime in North Korea."

Washington routinely condemns Pyongyang's nuclear and missile programs as violations of United Nations sanctions, and has taken the isolated nation to task for its human rights record. But it is rare for U.S. officials to directly question the rule of Kim, who took over after his father died in December 2011.