President Donald Trump's blockade of oil tankers coming in and out of Venezuela could have a damning effect on Cuba.

Cuba is already buckling under its most prolonged economic crisis in decades, with shortages so severe that many families are skipping meals and enduring long blackouts that leave people sleeping outdoors in sweltering heat, The Wall Street Journal reported.

Public health problems are worsening, garbage is piling up, and communicable diseases are spreading, the report said, as millions of Cubans have fled the island in what analysts describe as a humanitarian meltdown.

Now Havana's lifeline of subsidized Venezuelan oil  is under direct threat.

Trump is ratcheting up pressure on Venezuelan strongman Nicolas Maduro by targeting sanctioned tankers that carry a large share of the country's crude exports.

One tanker already seized by U.S. authorities was carrying nearly 2 million barrels of Venezuelan oil, according to the report.

If Venezuelan shipments stop or sharply decline, Cuba's communist rulers fear the consequences would be catastrophic.

"It would be the collapse of the Cuban economy, no question about it," Jorge Pinon, a Cuban exile who tracks energy ties at the University of Texas at Austin, told the Journal.

Venezuela has propped up Cuba since 1999, when then-President Hugo Chavez forged an ideological alliance with Havana.

In exchange for Cuban doctors, trainers, and intelligence operatives, Venezuela once sent roughly 100,000 barrels of oil a day.

That flow has dropped dramatically, but the Journal reported Venezuelan crude still covers a major share of Cuba's imported fuel, critical for power generation, transportation, and the private sector that has emerged despite communist resistance.

The crackdown on tankers comes alongside a broader U.S. pressure campaign against Maduro that the Journal said includes a major military buildup in the Caribbean, actions against vessels allegedly tied to narcotics trafficking, and sharper rhetoric meant to isolate the regime.

U.S. forces on Saturday stopped an oil tanker off Venezuela's coast for the second time in less than two weeks following the Dec. 10 seizure and Trump's announcement of a blockade of sanctioned tankers.

Homeland Security Secretary Kristi Noem said the Coast Guard, with support from the War Department, conducted what an official described as a "consented boarding" of a vessel called Centuries after it recently docked in Venezuela.

Venezuela's government called the U.S. action "criminal" and vowed to pursue legal avenues, including complaints to the U.N. Security Council.

One shipping expert suggested to The Associated Press that the vessel appeared properly registered, but said the move could be intended to deter other tankers from carrying sanctioned oil.

For Cuba, the stakes are existential.

The island's leadership is deeply invested in keeping Maduro in power, relying on Venezuelan oil and Cuban security influence inside Venezuela to keep the alliance intact.

The Associated Press contributed to this report.

• Cuba on Edge as US Seizure of Oil Tanker Puts Supply at Risk
• Trump Expands Travel Ban, Adding 5 More Countries and Imposing New Limits on Others