power play last week by US-backed opposition leader Juan Guaidó. But US officials have been more cautious in their predictions of Mr Maduro's swift exit, while re-assessing what one official described as the likelihood of a diplomatic "long haul".

US officials point to the president's sustained commitment to the Venezuela issue, from the first weeks of his presidency, as evidence that he holds a realistic view of the challenges there and does not think there is a quick fix. But Mr Trump has nonetheless complained over the last week that Mr Bolton and others underestimated Mr Maduro, according to three senior administration officials who spoke on the condition of anonymity.

Mr Trump has said Mr Maduro is a "tough cookie", and that aides should not have led him to believethat the Venezuelan leader could be ousted last week, when Mr Guaidó led mass street protests that turned deadly.

Instead, Mr Maduro rejected an offer to leave the country and two key figures in his government backed out of what Mr Bolton said had been a plan to defect.

Mr Maduro publicly mocked Mr Trump in response and said he wasn't going anywhere, saying the US had attempted a "foolish" coup.

On Wednesday, Venezuelan intelligence police detained National Assembly Vice President Edgar Zambrano in a dramatic operation in Caracas, marking the first senior opposition official taken into custody by the socialist government in retaliation for the failed military uprising.

Independent News Service