Donald Trump’s top Latin America adviser has claimed “there is not a single scenario” in which Nicolás Maduro and his “cronies” are able to retain power in Venezuela.

The revolt against Maduro’s regime is entering its fourth week, with the Venezuelan strongman showing no sign of relinquishing power despite a startling and largely unforeseen challenge from a previously obscure opposition leader called Juan Guaidó.

An anticipated large-scale military abandonment of Hugo Chávez’s heir has not materialized despite Guaidó – who is now recognized as Venezuela’s legitimate interim president by most western governments – repeatedly touting an amnesty for the armed forces.

However, in an interview with Latin American journalists in Washington, the National Security Council’s senior director for western hemisphere affairs insisted Maduro’s demise was a foregone conclusion.

“The path we are going down is irreversible … The question is no longer if Maduro accepts this or not, it’s how long it will take him to accept it,” Mauricio Claver-Carone said.

Claver-Carone, a conservative Cuban-American lawyer, renewed US calls for Venezuela’s military top brass to ditch Maduro, claiming the White House would not “persecute” those who backed “a peaceful and democratic transition”. “We are not in the business of revenge, nor are we seeking to settle scores.”

Maduro’s domestic and international foes are adamant he is doomed. Colombia’s foreign minister, Carlos Holmes Trujillo, last week branded Maduro’s regime “an unburied corpse”.

But many observers believe Guaidó’s opposition movement will be frustrated not to have seen more military defections.

With a new round of opposition protests planned for Tuesday, Venezuela expert Moisés Naím admitted it was impossible to predict Maduro’s fate.

“We are living in maximum uncertainty. He could be gone tomorrow or he could be around for the next few months,” said Naím, a fellow at the Carnegie Endowment for International Peace and former Venezuelan minister.

And whatever happens to Chávez’s heir, it is not guaranteed his regime would fall with him, with some believing a rival Chavista could emerge as an internal challenger.

“One scenario is that Maduro leaves, but the regime stays,” Naím said, pointing to what he believed was a fierce and long-running behind-the-scenes struggle for control of Chavismo.

“It is a battle of the socialist billionaires for survival.”

Nicmer Evans, a longtime Chavista who split with the movement in 2013, agreed that while Maduro was down, the political movement he inherited after Chávez’s 2013 death was not yet out.

“Maduro might kill [Chavismo] but it’s still not dead. It’s in critical condition. It’s a wounded animal. It’s in power, it can respond, it is capable of harming – but it is agonizing,” Evans said.

Maduro has been hit hard by sweeping US oil sanctions intended to asphyxiate his regime although Venezuela’s state-run oil giant, PDVSA, is reportedly now asking customers to make payments into a newly opened account in Russia in order to sidestep those prohibitions.

Another challenge is expected in the coming days with opposition leaders currently stockpiling US humanitarian aid on the Colombian border which they vow to bring into Venezuela.

On Friday, Maduro insisted the aid convoy would not be allowed in, calling it a “a rotten gift” and an imperialist military provocation designed to destabilize his government.

Speaking in Caracas on Sunday, Guaidó urged the military to ignore Maduro’s “ridiculous” order to block the aid. “Today we can save lives in Venezuela,” he told reporters.

Guaidó echoed Claver-Carone’s claim that time was running out for Maduro. “Every day that passes … is a victory for democracy that brings us closer to the freedom of Venezuela.”