Shannon, 57, who led a similar rapprochement last year that stalled over imprisoned protest leader Leopoldo Lopez, also met with opposition figures and civil society activists on his short visit to Caracas.

During 17 years of socialist rule under Maduro and his predecessor Hugo Chavez, Venezuela has replaced Cuba as Washington's principle irritant in the Americas.

The US is backing an opposition push to hold a "fair and timely" referendum this year that could see Maduro ousted.