US national security adviser, John Bolton, has insisted Venezuela’s “tired dictator” was at “the end of his rope”, as he opened another front in the White House’s economic blitz on Nicolás Maduro by freezing all Venezuelan government assets in the United States.

Addressing a summit on Venezuela’s crisis in Peru’s capital, Lima, Bolton pronounced Maduro’s “dying regime” doomed – even though a seven-month US-backed campaign has so far failed to topple Hugo Chávez’s authoritarian successor.

Bolton claimed Donald Trump’s latest moves – which will also see those who do business with Maduro’s government sanctioned – would help end “Maduro’s tyrannical reign”.

“The time for dialogue is over. Now is the time for action,” Bolton declared, spurning Norway-sponsored negotiations that have been taking place between representatives of Maduro and his US-backed challenger, Juan Guaidó.

But experts questioned the impact and wisdom of the measures, which Maduro’s administration and its Russian backers branded “economic terrorism”.

Some fear the latest sanctions will further aggravate an already dire humanitarian situation which has already forced millions to flee Venezuela, while others believe they will alienate Guaidó’s European backers who believe a negotiated solution is possible.

Christopher Sabatini, a senior fellow for Latin America at the Chatham House thinktank, said Trump’s latest gambit was designed to achieve nothing but Maduro’s immediate downfall.

“This is intended to bring this government to its knees and to bring in Guaidó. That’s it … But it will not work. It will actually make Maduro’s government what it always wanted to be: a martyr,” Sabatini said.

Farid Kahhat, a professor of international relations at Lima’s Catholic University, said that while Maduro was to blame for Venezuela’s economic meltdown, “what the US is doing is making things worse – at least in the near future”.

Addressing a regional bloc known as the Lima Group and other members of the pro-Guaidó international coalition, Bolton urged China and Russia – Maduro’s key patrons – to abandon their “intolerable” support for his administration.

“It’s time to bring Maduro’s tyrannical reign to a peaceful end for the benefit of the entire western hemisphere,” he said.

But David Smilde, a Venezuela expert from the Washington Office on Latin America advocacy group, said for all Bolton’s “soaring, inspirational rhetoric”, the new sanctions were unlikely to prove a game-changer.

“He’s been saying the same thing for a long time.”

Eric Farnsworth, a former US diplomat and vice-president of the Council of the Americas, said the US moves were partly an attempt to signal that efforts to unseat Venezuela’s strongman leader had not “plateaued”, as well as to further undermine Maduro.

“Obviously the goal here is to get Maduro out of power … [But] I don’t now what the trigger is to force him out – I don’t think anybody does. That’s part of the issue,” he admitted.

In a statement Venezuela’s foreign minister, Jorge Arreaza, denounced Trump’s “new and serious aggression” against Maduro’s administration, claiming it was designed to inflict “severe wounds on Venezuelan society” and force regime change.

Sabatini said he was concerned that in its campaign to remove Maduro, the US was relying too much on its stick and not enough on carrots.

“All you have is a stick – and you are beating the hell out of Venezuela and beating your own allies,” he said. “This makes no sense.”