HAVANA — Cuba reconnected its power grid on Tuesday and brought online its largest oil-fired power plant, energy officials said, putting an end to a nationwide blackout that lasted more than 29 hours amid a US move to choke off the island's fuel supply.

After the country's 10 million people had been plunged into darkness overnight, the Caribbean island's national power grid came fully back online by 6:11 pm. However, officials said power shortages may continue because not enough electricity is being generated.

In addition to cutting off oil sales to Cuba, US President Donald Trump said on Monday he could do anything he wanted with the country.

A US State Department official blamed the Cuban government for the grid collapse.

Cuban President Miguel Diaz-Canel fired back at Washington, criticizing its "almost daily public threats against Cuba".

"They intend to … announce plans to take over the country, its resources, its properties, and even the very economy they seek to suffocate in order to force us to surrender," Diaz-Canel wrote on social media on Tuesday night, shortly after power returned nationwide.

Cuba has yet to say what caused Monday's nationwide grid failure, the first such collapse since the United States cut off Cuba's oil supply from Venezuela and threatened to slap tariffs on countries that ship fuel to the island nation.

By midday on Tuesday, grid workers successfully fired up the Antonio Guiteras power plant, a decades-old behemoth that underpins the country's power grid.

Electricity generation, hampered by dire fuel shortages and antiquated power plants, is still far below what is necessary to cover demand, providing scarce relief for Cubans already exhausted from months of blackouts.

Cuba's government is under increasingly crushing pressure, with Washington enforcing an oil blockade and openly stating it wants to end the nearly seven-decade-old US standoff with the state.

US Secretary of State Marco Rubio said Cuba's decision announced this week to let exiles invest and own businesses did not go far enough to allow free-market reforms that the US administration had demanded. "What they announced yesterday is not dramatic enough. It's not going to fix it. So they've got some big decisions to make," Rubio told reporters at the White House.

Trump said on Monday he would "take" Cuba, adding: "We'll be doing something with Cuba very soon."

But his Cuban counterpart Diaz-Canel was defiant in the face of Washington's threats.

'Unbreakable resistance'

"Faced with the worst-case scenario, Cuba has one guarantee: any external aggressor will encounter an unbreakable resistance," he wrote in a statement on X.

Cuba is open to broad talks with Washington and allowing more investment, but it will not discuss changing its political system, an envoy told AFP on Tuesday.

Tanieris Dieguez, Cuba's deputy chief of mission in Washington, said the two neighboring countries "have a lot of things to put on the table", but that neither should ask the other to change its government.

"Nothing related with our political system, nothing with our political model — our constitutional model — is part of the negotiations, and never will it be part of that," she said.

"The only thing that Cuba asks for (in) any conversation is respect to our sovereignty and to our right to self-determination."

The New York Times reported on Monday that US officials have asked Cuba to remove the president but have not pushed for a complete toppling of the government.

Rubio on Tuesday denied the report.

In a late-night post on X, Rubio said the article was "fake" and was among media reports that relied on "charlatans and liars claiming to be in the know" as sources.

The Russian Foreign Ministry on Tuesday voiced serious concern over the mounting US pressure on Cuba, pledging necessary support for the nation.

"There has been a deliberate effort to ratchet up the atmosphere of confrontation," the ministry said in a statement on its website.

"We firmly condemn attempts to grossly interfere in the domestic affairs of a sovereign state," it said.

Agencies - Xinhua