Cuban President Miguel Díaz-Canel on Wednesday blamed a U.S.-imposed "genocidal energy blockade” for worsening already grim electricity shortages across the island.
The island's power supplies are dropping to new lows, data compiled by AFP showed, with prolonged blackouts and record generation shortfalls in recent days.
Sixty-five percent of Cuban territory endured simultaneous blackouts on Tuesday, according to the data.
Diaz-Canel acknowledged the "particularly tense" situation in an X post.
"This dramatic worsening has a single cause: the genocidal energy blockade to which the United States subjects our country, threatening irrational tariffs against any nation that supplies us with fuel," he said.
The island's ongoing energy crisis worsened in January when the United States imposed an oil blockade on the island of 9.6 million people.
Since then, only one Russian tanker has reached Cuba, which is in the throes of economic stagnation and supply shortages.
Outages of more than 19 hours a day are being reported in Havana, while in several provinces, blackouts last for entire days, meaning that most Cubans spend more time without power than with it.
The current period of difficulty reflects deteriorating conditions that had slightly improved in April following the arrival of the Russian tanker.
Cuba's electricity generation is sustained by a network of eight aging thermoelectric plants, some in operation for over 40 years, that suffer frequent breakdowns or must be shut down for maintenance cycles.
Cubans have endured seven nationwide blackouts since 2024, including two in March, and fuel prices have soared.
US renews aid offer
Also on Wednesday, the U.S. renewed an offer of $100 million in aid for Cuba.
Secretary of State Marco Rubio, speaking last week in Rome, said that Cuba had rejected an offer of $100 million in assistance, an assertion denied by the communist government in Havana.
The State Department on Wednesday publicly renewed the proposal, which comes after the United States piled new sanctions against key parts of Cuba's state-controlled economy.
"The regime refuses to allow the United States to provide this assistance to the Cuban people, who are in desperate need of assistance due to the failures of Cuba's corrupt regime," the State Department said.
"The decision rests with the Cuban regime to accept our offer of assistance or deny critical (life)-saving aid and ultimately be accountable to the Cuban people for standing in the way of critical assistance," it said.
It said that the support would include direct humanitarian assistance from the United States and funding for "fast and free" internet access -- which presumably would benefit dissidents in the one-party state that restricts media.
The United States, the statement said, was working to promote "meaningful reforms" in Cuba.
President Donald Trump's administration already provided $6 million in humanitarian aid to Cuba but channeled it through the charity of the Catholic Church, which has long played a go-between role for the two countries.
After Rubio's initial comments, Foreign Minister Bruno Rodriguez said the offer was a "lie" that "no one here knows anything about."
"Will it be a donation, a deception or a dirty deal to curtail our independence? Wouldn't it be easier to lift the fuel blockade?" Rodriguez wrote on X.
Rubio, a Cuban-American who vociferously opposed the communist system founded by Fidel Castro, has been widely reported to be in contact with segments of the Cuban elite in hopes of stirring change.
Trump has publicly mused about taking over the island, which has been under a U.S. embargo almost continuously since Castro's 1959 revolution.
Cuba's economic woes intensified in January after the United States deposed Venezuela's leftist leader Nicolas Maduro, whose government had been providing around half of the island's fuel needs.
Last week the United States imposed sanctions on a Cuban military conglomerate that controls nearly 40% of the economy, after Trump signed an order to punish any foreign banks that transact with U.S.-blacklisted entities.