US President-elect Donald Trump has announced the launch of a new anti-drug advertising campaign to highlight the impact of drug use.

Trump said his administration would spend "a lot of money" on the program, but that it would be "a very small amount of money, relatively speaking." His plan has echoes of the "Just Say No" anti-drug campaign led by former Republican first lady Nancy Reagan in the 1980s. Trump also reiterated his pledge to designate Mexico's drug cartels as terrorist groups.