Washington (AFP) - Facing a crisis in Venezuela, US President Donald Trump has threatened to inflict "swift and strong" economic sanctions unless President Nicolas Maduro backs away from a plan to rewrite that nation's constitution.

But the American president seems sure to face a backlash from Caracas, where charges of US "imperialism" have been the socialist government's favorite retort to pressure from the North.

Trump, like his predecessor Barack Obama, confronts the difficult task of managing the long-toxic relationship between the two countries. The two have not had ambassadors in each other's capitals since 2010.

But while Obama's Democratic administration succeeded in at least slightly lowering tensions, the relationship has dramatically soured since billionaire Republican Trump came to office in January.

"All options are on the table," senior White House officials said late Tuesday, underscoring the toughly worded warning Trump himself had issued a day before.

"The United States will not stand by as Venezuela crumbles," Trump said in a statement Monday. "If the Maduro regime imposes its Constituent Assembly on July 30, the United States will take strong and swift economic actions."

- 'Becoming a dictator' -

The American president called his Venezuelan counterpart a "bad leader who dreams of becoming a dictator."

And senior administration officials who briefed reporters Tuesday denounced what they called the "dictatorial" regime in Caracas and demanded a "re-establishment" of democracy.

In the US Congress, Republican Senator Marco Rubio recently demanded "the full restoration of the democratic order and respect of basic rights in Venezuela as the regime of Nicolas Maduro continues its assault on the Venezuelan people and the country’s democratic institutions."

Pro- and anti-Maduro demonstrations in Venezuela have left nearly 100 people dead since April 1, amid the near-collapse of the oil-rich nation's economy and steps by Maduro that opponents say amount to a power grab.

Both the White House and several American lawmakers expressed support for the symbolic vote last weekend in Venezuela, sponsored by the opposition, that saw 7.6 million people demand an end to plans for a Constituent Assembly -- which Maduro's opponents say would be set up to favor him -- to draw up a new constitution.

Moises Rendon, an analyst with the Center for Strategic and International Studies (CSIS) in Washington, wrote in a recent paper that "the single most important action for the United States, regional countries and the world is not to recognize the government that comes out from the illegitimate Constituent Assembly," which he described as "Soviet-style."

But some analysts warn that too hard a line from the United States could backfire.

Geoff Thale, with the lobbying group Washington Office on Latin America (WOLA), told AFP he was "very skeptical that unilateral US sanctions (would be) effective. They are more likely to make the government feel they have no option but to resist, and they offer the government a nationalist rallying cry against the US."

- 'People will starve' -

David Smilde, a Venezuela specialist at Tulane University in New Orleans, Louisiana, said, "I believe it is possible that the Venezuelan government will be strengthened by US sanctions. There is no way to apply economic sanctions now in Venezuela without making the humanitarian situation much worse. People will starve to death."

US sanctions, he added, "would unleash enormous resentment among the Venezuelans" and would "never be well received by other countries in the region."

US involvement in Latin America carries enormous luggage. The United States has long been accused of interventionism -- even "imperialism" -- in what Washington has sometimes viewed as its "backyard."

Maduro, for his part, has threatened a "very firm" response to the "imperial threat" from his American counterpart. His foreign minister, Samuel Moncada, denounced what he called "the insolent threat of a xenophobic and racist empire."

But even as the diplomatic temperature between the two countries hovers near zero, economic relations have long been close: The United States remains the leading importer of Venezuelan oil, and several American multinationals, including automaking giant General Motors, have invested heavily for decades in what they viewed as a southern El Dorado.

The White House officials who briefed reporters on Tuesday seemed aware of the potential impact US economic sanctions could have on American business.

In Smilde's view, punitive new US measures -- following sanctions taken in February by the Trump administration against Venezuelan Vice President Tareck El Aissami, accused of trafficking in drugs -- could even push Caracas into the arms of "Russia and China."