Donald Trump’s recent mention of a potential Venezuelan military coup against leftist President Nicolas Maduro was taken as a signal of support for action against a regime "that frankly could be toppled very quickly," in the words of the U.S. president.

“We want to leave their military in no doubt that Trump would support a coup,” a White House advisor told Fox News, acknowledging U.S. officials had secretly spoken with dissident officers and opposition members seeking to remove Maduro by force.

Sources with the Pentagon and in Venezuela’s military say several coup attempts have already been staged, including an assassination bid using explosives-packed drones in August. Ex-Venezuelan police official Salvatore Lucchese, who claims to have had a role in planning some attacks, told Reuters there is a “sustained armed movement against the regime composed of street activists, students and ex-military officers.”

But several analysts consulted by Fox News warned removing Maduro won't be easy, and that further attempts may result in a wider-scale conflict.

Maduro has so far managed to dismantle a series of plots with the aid of Cuban, Russian and some Iranian security advisors, who manage extensive surveillance systems, internal spy networks and paramilitary militias comparable to those in the world's most repressive police states.

“It‘s difficult to structure a coup because much of the high command is compromised through corruption, and the military are being subordinated to politically directed militias and internal controls managed by Cubans,” said Ivan Carratu, a former admiral in the Venezuelan Navy. Officials told Fox News Venezuela also has a sophisticated signals intelligence base operating on the island of Orquidea, off the northern coast of Venezuela.

A move against Maduro would likely be coordinated with the U.S. Southern Command, according to Carratu, who said the Venezuelan Navy is ready to act, but the army is more ambivalent. “If the armed forces split, it could mean civil war,” he warned.

Pentagon officials who spoke on condition of anonymity denied there is an ongoing plan for U.S. intervention in Venezuela. But “we would take advantage of a major uprising or coup attempt," a source said.

A U.S. intervention might take place in the event of a total collapse of order, or if the regime attacked a neighbor like Colombia, a close U.S. ally.

More than two million Venezuelan refugees escaping hunger, and repression have flooded into neighboring countries, generating a humanitarian crisis some compare to Syria’s. Some Latin American governments and opposition leaders have accused Maduro of “genocide” at international forums.

Trump’s repeated insistence that “all options are on the table” to remove Maduro has been attacked as sabre-rattling by the mainstream media, and most experts are urging caution. “The U.S. would have to work closely with the Venezuelan military. Anything that smacked of invasion would trigger seriously adverse international reaction,” said Nigel Inkster, of London’s International Institute of Strategic Studies.

Venezuelan Foreign Minister Jorge Arreaza has warned a war in Venezuela would “make Vietnam look small.” In addition to the regular armed forces, Venezuelan officials claim to have hundreds of thousands of men and women in militias, ready to rise up in arms for the regime.

Trump asked the U.N. General Assembly to “join us in calling for the restoration of democracy in Venezuela”. But Russia and China would be sure to veto any resolution against Maduro, who has mortgaged much of Venezuela’s oil reserves to them. Venezuela has also purchased billions of dollars in Russian armaments.

But support for U.S. intervention may be growing in Latin America, where OAS Secretary-General Luis Almagro has recently echoed Trump’s statements about keeping military options open. Newly elected conservative presidents in Colombia and Brazil also want to oust Maduro.

Successive National Security Council officers formulating the administration’s views on Latin America have been “hawkish” on Venezuela, according to Ewan Ellis, an area specialist with the U.S. Army War College. At least two who have come from the CIA’s analysis division were described as “highly focused” on Venezuela, by a Pentagon official who worked with them.

The Obama administration, by contrast, gave Venezuela low priority. It dismantled an interagency task force created by President G.W. Bush to investigate the regime’s ties with Iran, despite evidence that Qods officers and Hezbollah cells were active there.

As a result of past neglect, “we are below the intelligence curb in Venezuela”, said Joseph Humire, a Latin America specialist who lectures U.S. special forces units targeted on Latin America. Russians Cubans and Iranians advising Maduro can “blind and misdirect us," Humire said.

Sources told Fox News some 300 Venezuelan army, navy and air force officers have been arrested under suspicion of being involved in coup plotting. And many of those have been tortured, according a Venezuelan military lawyer who has been in contact with jailed officers. The lawyer has a list of 152 who are being prosecuted for mutiny and rebellion, including Capt. Luis de la Sotta, who headed Venezuela’s equivalent to the U.S. Navy Seals.

The U.S. charge d’afairs and another embassy diplomat were expelled from Venezuela following a roundup of military dissidents last May, accused of colluding in coup conspiracies.