The unexpected move is being widely reported as part of US efforts to break the large oil producer from "Russia's influence" at a moment the White House and Europe are trying to economically and politically isolate Putin. 

It likely came as a surprise to Maduro himself - given that not only has Washington long recognized opposition leader Juan Guaidó as 'Interim President' of the country, but has multiple times in recent years actually seized fuel shipments bound for Venezuela (from Iran), while also seeking to block Venezuela's crude exports and seize some state assets.

During the last two years of the Trump administration, there was even talk of using the US Navy to impose a full oil embargo against the Latin American socialist country - and prior to that, short-lived attempts to foment local uprising among the military in an aim to overthrow Maduro. 

The trip was made public Sunday via unnamed US administration officials, but wasn't immediately confirmed by the White House. It evoked outrage among Venezuela hawks, most notably Marco Rubio: