The National Assembly has stepped up the pressure this month in its power struggle with Maduro and his regime, calling for a mass people's protest next week, reaching out for international support and offering "amnesty" to those in the military that disavow Maduro.

Led by the its 35-year-old president, Juan Guaido, the legislature is embarking on an ambitious bid to wrestle back the power it was stripped of in 2017 by a Supreme Court filled with Maduro loyalists.

Success, though, depends on support from one entity more than any other.

"The key is the armed forces, which is guided by a leadership that fears losing its political and economic influence, and a change of government" that would remove its protection against prosecution "for corruption and human rights violations," Diego Moya-Ocampos, an analyst at London based consultants IHS Markit, told AFP.

Parliament has declared Maduro a "usurper" while Guaido claims the Venezuelan constitution allows him to assume power and set up a transitional government ahead of elections.

But with the Supreme Court annulling every decision the legislature makes, and the military high command declaring "loyalty" to Maduro when he was sworn in for a second six-year term on January 10, the National Assembly is lacking in domestic might.

"The opposition is relaunching its strategy, but it needs a lot more than a constitutional base to achieve change," added Moya-Ocampos.

"It needs a more determined support from the international community and for the protests to make the armed forces and apparatus of repression cave in."

The scale of the opposition's public support will be seen on January 23 -- the day in 1958 that the military dictatorship of Marcos Perez Jimenez fell -- when it has called for a mass protest against Maduro.

The government has responded by calling for a counter demonstration in support of the president.

It will be the first such mass street action since 125 people were killed in protests between April and August 2017.

- 'No imminent rupture' -

Influential international entities such as the United States, European Union and Organization of American States (OAS) have made encouraging noises.

OAS general secretary Luis Almagro called Guaido Venezuela's "acting president" while the US and Brazil offered him encouragement, while describing Maduro as "illegitimate."

But despite the socialist leader's increasing international isolation, "an internal rupture is not imminent," the Eurasia Group consultancy said.

The National Assembly retains hope, though, and has been trying to woo domestic support from the "middle and low-ranking" military and government officials.

Guaido saw signs of progress on Sunday when he was briefly detained by intelligence service agents, only for the government to deny any knowledge of the operation, accusing the opposition of staging the incident and claiming to have fired the police involved.

"Who is commanding the regime now? If they're already admitting that they don't control the state's security agencies, there's a serious problem," said Guaido.

The National Assembly has been reaching out to foreign countries to help starve Maduro's regime of any funding in a bid to crank up the pressure.

On Tuesday, parliament wrote to 46 countries, including Maduro allies Russia, China and Turkey, asking them to prohibit the handling of funds, accounts and assets belonging to the Venezuelan state.

- Continued US support -

The US has said it will consider toughening its sanctions against top Venezuelan regime figures, as well as the state oil company PDVSA.

So far, Washington has banned its citizens and businesses from negotiating new debt for the country and the state energy supplier, and has imposed individual sanctions on Maduro, his wife and many top officials.

Guaido's brief detention -- which lasted less than an hour -- has raised his profile, with US Vice President Mike Pence speaking with him by telephone on Tuesday, and promising "continued support" from Washington.

But the challenge remains huge, not least because the opposition is disunited, with many leaders either jailed or exiled, or even lacking credibility in the eyes of their own supporters.

"International recognition" of Venezuela's parliament and "support for Guaido could make the opposition a more relevant actor in a political transition," Eurasia Group said.

"But it remains deeply divided with little ability to deliver political change."

For analyst Luis Viucente, "it's easy" for the opposition to talk about demanding Maduro leave, but the "true challenge" is to unite behind "a real strategy, a plan of action and a united leadership."

And that's something that has so far been lacking from the opposition.

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