President Trump threatened Tuesday to impose a “full and complete embargo” and more economic sanctions on Cuba if that government does not end what Trump called deadly intervention in Venezuela, where soldiers and opposition forces clashed in the streets in what U.S. officials said may be a pivotal uprising.

Secretary of State Mike Pompeo said in an interview that Venezuelan President Nicolás Maduro had planned to step down and leave the country until his ally Russia persuaded him to stay.

The chaos in Caracas indicated that, while a plan had been in motion, it may not have unfolded as anticipated. There were indications that opposition leader Juan Guaidó’s call for military defections and widespread demonstrations were expected Wednesday, rather than Tuesday. Announcements by senior Maduro officials that they were changing sides did not materialize, and the administration appeared increasingly concerned as it debated next steps.

In Washington, opposing groups skirmished at the Venezuelan Embassy, and Guaidó’s ambassador to Washington told reporters that “this is the beginning of the end.” Both Republican and Democratic lawmakers voiced support for the interim Guaidó government.

Trump and national security adviser John Bolton warned of heavy U.S. retaliation against Cuba, whose anti-capitalist government is closely linked with the socialist government in Venezuela.

“If Cuban Troops and Militia do not immediately CEASE military and other operations for the purpose of causing death and destruction to the Constitution of Venezuela, a full and complete embargo, together with highest-level sanctions, will be placed on the island of Cuba. Hopefully, all Cuban soldiers will promptly and peacefully return to their island!” Trump wrote in a pair of tweets late Tuesday.

Bolton accused Cuba of playing a “direct role in propping up the failed Maduro regime in Venezuela,” and Pompeo suggested that Russia and Cuba had acted in concert to thwart what might have been Maduro’s peaceful abdication.

“He was headed for Havana,” Pompeo said in the CNN interview late Tuesday. Pompeo did not spell out exactly when Maduro supposedly had decided to go and when he changed his mind. Pompeo also would not say how the U.S. government knew of the developments.

“Fire up the plane,” Pompeo advised Maduro, suggesting that Maduro would have safe passage out of the country. “He knows our expectations.”

Speaking later on Fox News, Pompeo said the United States had been urging Maduro to step down and leave peacefully “for some time,” but he did not elaborate.

The Trump administration accuses Russia and Cuba of propping up Maduro while trying to blame Washington for the collapse of the Venezuelan economy.

“We will continue to take actions to cut the Cuban regime’s lifelines in Venezuela and hold it accountable for the destabilizing role it plays in this man-made crisis,” Bolton wrote on Twitter.

Trump’s warning appeared to refer to a return to the full U.S. embargo on Cuba that President Barack Obama partially lifted in a bid to improve ties. Trump has already reversed many elements of Obama’s attempted diplomatic opening.

Earlier Tuesday, Bolton had told reporters that Trump is watching political developments in Venezuela “minute by minute.” Bolton also put unusual public pressure on individual Venezuela government officials to renounce Maduro and embrace the political opposition.

Speaking as government loyalists clashed with opposition forces in the streets of the Venezuelan capital, Caracas, Bolton told reporters that the fast-moving events Tuesday, which included defections of at least some military forces, constitute a “potentially dispositive moment in the efforts of the Venezuelan people to regain their freedom.”

“It’s a very delicate moment,” Bolton said. “The president wants to see a peaceful transfer of power,” which he added would be possible if enough military and government figures switch allegiances.

Bolton repeated that “all options” remain open to Trump but said nothing further about any potential use of U.S. military force. He warned Russia not to interfere in the unfolding events and repeatedly accused Cuba of fomenting violence.

In an apparent attempt to divide Maduro’s government, Bolton said senior officials, including Defense Minister Vladimir Padrino López, had been in secret talks with Guaidó, and he called on them to “make good on their commitments” to help oust Maduro.

Earlier in the day, however, Padrino appeared on live television in Venezuela, surrounded by dozens of military commanders and troops. Dressed in combat fatigues and body armor, and standing beneath a massive portrait of Maduro, Padrino described the number of military personnel who appeared with Guaidó as “a small group, minuscule, of military and police officials who decided to kidnap a few national guard vehicles and some arms and ammunition.”

The United States was the first among about 50 countries to recognize Guaidó as the legitimate interim president of Venezuela.

“This is clearly not a coup,” Bolton said, adding that Guaidó has the authority to direct the military.

Guaidó appeared in a video early Tuesday flanked by some military figures and accompanied by a leading opposition figure, Leopoldo López, who had been under house arrest. The video and the apparent military involvement in freeing López led to optimism within the Trump administration that it has bet correctly that the powerful Cuban-backed military would eventually turn against Maduro and policies that are bankrupting the once-rich country.

“I am monitoring the situation in Venezuela very closely. The United States stands with the People of Venezuela and their Freedom!” Trump tweeted after Bolton’s impromptu news conference outside the White House.

The Republican administration’s opposition to the socialist Maduro has a strong ideological component, and Trump often accuses Democrats of pursuing an agenda that would turn the United States “into Venezuela.”

Bolton called by name for three officials in Venezuela — the defense minister, the chief judge of the Supreme Court, and the commander of the presidential guard — to support Guaidó taking power.

“Your time is up. This is your last chance,” Bolton tweeted. “Accept Interim President Guaido’s amnesty, protect the Constitution, and remove Maduro, and we will take you off our sanctions list. Stay with Maduro, and go down with the ship.”

His suggestion that Padrino, in particular, had pledged to flip on Maduro was startling. It followed Padrino’s 19-minute address, in which the defense chief had called the street uprising “a coup.”

“We say to the people of Venezuela and to the entire world that this fact of violence against the peace of our citizens, it has failed,” he said.

A senior Latin American official said opposition talks had been going on with Padrino and the other two for “the last several weeks,” and that the three had been promised retention in their current positions if they came out publicly in support of “constitutional order” that would allow Guaidó to take power. The official, who spoke on the condition of anonymity about the fast-moving and confusing situation, said those involved in the negotiations had no initial explanation for what went wrong, and compared it to an aborted aid convoy earlier this year from Colombia to Venezuela that Guaidó backers believed would lead to a nationwide uprising and Maduro’s departure.

In the months since the administration recognized Guaidó as Venezuela’s legitimate leader, as the crisis has dragged on without resolution, the administration has turned to Cold War rhetoric, blaming Cuba and Russia for Maduro’s staying power. Russia, along with China, has provided Venezuela with tens of billions in loans — often in exchange for equity in Venezuelan oil fields. But while the Kremlin has used Venezuela to taunt the United States, and its investment and support to keep Maduro under its thumb, administration officials appear confident that Moscow has little interest in a military confrontation in faraway South America.

It is Cuba that has drawn the brunt of U.S. criticism. Under a decade-old agreement, Venezuela has supplied cash- and energy-strapped Cuba with free and subsidized oil, in exchange for sending more than 20,000 Cubans to Venezuela. Havana says they are doctors and teachers, while the U.S. administration says they are primarily military and intelligence agents. They are, according to the administration, the “enforcers” who keep the Venezuelan military from flipping to support Guaidó.

Cuban control of the intelligence service, and of communications among military leaders, is believed to have kept the Venezuelan military from organized opposition to Maduro. But the Cubans risk economic and military disaster if they continue supporting him. Trump has already imposed sanctions to cut off Venezuelan oil shipments to the island, and Tuesday’s threat of a “full and complete embargo” may leave Havana in the position of having little beyond rhetorical weapons.

Elliott Abrams, the administration’s special envoy for Venezuela, told reporters Tuesday that the United States had expected Padrino, along with the head of the Maduro-appointed Supreme Court and the head of the national guard, to declare their support for the Venezuelan constitution, if not necessarily for Guaidó himself.

“We urge the Venezuelan military to stand up for the nation, and for the constitution, and stand behind the people of Venezuela,” he said. “They will be judged by their actions today.”

Abrams said U.S. officials had been expecting big May Day-themed marches on Wednesday and said U.S. officials did not know the plans had been pushed up by a day.

He said that opposition figures had held discussions with the three influential officials in Maduro’s government ahead of those planned demonstrations.

Abrams said the United States was not involved in the discussions, which he said were all among Venezuelans.

Asked whether naming them put them in danger, Abrams said, “I don’t think they’re in danger, for one thing, if constitutional order is restored to Venezuela. And as I recall the agreements, all of them were going to retain their positions.”

Abrams said he had exchanged text messages with Guaidó on Tuesday afternoon, describing him as “buoyant and determined.”

Asked whether Guaidó is likely to be arrested, Abrams said an arrest would not solve Venezuela’s problems.

Carlos Vecchio, Guaidó’s ambassador to the United States, also said Monday that the opposition leadership had had “conversations with part of the inner circle of Maduro” and that “they know that Maduro is not going anywhere. That Maduro is the past . . . and that’s why they want to look for a different future for Venezuela.”

Vecchio, speaking in an interview with the BBC, said that “we need to keep pressure on the street” to help convince senior government and military people that this is the time for them to switch sides.

Pompeo addressed the political developments but did not detail U.S. plans in Venezuela as he held a previously scheduled meeting Tuesday with Republican senators, participants said.

“Anything that happens to Guaidó, by the Maduro government, we hold you accountable,” Sen. Lindsey O. Graham (R-S.C.) said after the session. “Maduro would be gone a long time ago if it weren’t for the Russians,” he said.

“We need to put Cuba and Russia on notice that if any violence is directed toward Guaidó to try to arrest him or kill him, then we’re going to hold Russia and Cuba liable, and we will respond appropriately, and all options are on the table.”

As leaders around the world weighed in on Twitter, Cuban President Miguel Díaz-Canel tweeted that Cuba stood together “with the legitimate government of Venezuela, that is facing with serenity and courage a new coup attempt by the pro-imperialist right, with the complicity of the United States and its lackeys in the region.”

Asked whether the administration had spoken with Russia about the latest events, Bolton suggested that the U.S. position was already clear.

“We’ve made it clear to Russia in both public and private statements . . . that we regard the actions they’ve taken in Venezuela as something we regard with the utmost seriousness” and have emphasized that civilians should not be harmed.

The Russian Foreign Ministry has condemned what it called violence and incitement on the part of the Venezuelan opposition.

Karoun Demirjian and Carol Morello contributed to this report.