Recently Donald Trump announced via his Twitter feed that the US would be implementing new punitive tariffs on steel imports (at 25%) and aluminum imports (10%) to the US. Although highly unusual for a President to announce such policies via social media, Trump likes to see himself as different, and a master negotiator.
The visit was publicized by a senior State Department official as a follow-up to Secretary Tillerson's hastily-arranged and poorly-attended meeting with African foreign ministers in Washington in November 2017. Although the ministerial meeting covered trade, development and security issues.