BUENOS AIRES, Argentina — Argentine President Javier Milei escalated his country’s dispute with Britain over the Falkland Islands on Thursday, vowing new measures to halt an oil project near the British-controlled archipelago and praising U.S. President Donald Trump for saying Washington could reconsider its neutral stance on the islands’ sovereignty.

Milei cast Trump’s comments as proof that his close relationship with the U.S. president — criticized by political opponents as overly deferential — was paying dividends.

“The United States is considering this change in position because it knows that Argentina has a reliable partner, aligned with Western values, in a strategically important position that can be a valuable ally in the decades to come,” Milei said in a nationally televised speech.

The Argentine leader then announced sweeping actions aimed at stopping the development of the deep-sea Sea Lion oil project, about 220 kilometers (140 miles) north of the islands, where British company Rockhopper Exploration and Israel’s Navitas Petroleum plan to begin drilling in the coming months and start pumping oil in 2028. Argentina considers the project an illegal exploitation of resources in waters it claims as its own.

He threatened tougher sanctions against companies involved in the offshore drilling and announced new funding for a naval base in Argentina’s southernmost province of Tierra del Fuego to bolster the country’s military presence near the islands, known in Argentina as the Malvinas.

“Argentina will not stand idly by,” Milei said. “Any further advance on the Malvinas Islands will be considered a violation of our national security.”

Milei’s effort to refocus attention on the Falklands are a striking turn for a leader who has faced criticism at home for warming ties with Britain and professing admiration for Margaret Thatcher, the British prime minister detested in Argentina for leading the campaign to retake the archipelago during the 1982 Falklands War.

The two-month conflict, which killed 649 Argentine troops, 255 British service members and three islanders, remains a sore point in Argentina over four decades later.

The sovereignty claim is enshrined in Argentina’s constitution and frequently invoked as an expression of national identity, from banknotes to World Cup soccer chants. It is also one of the few causes that cuts across the country’s stark political divides, giving Milei, who is up for reelection next year, a welcome political opening as his approval ratings slip and the economy sputters.

“We can argue about my style. We can disagree over fiscal or exchange-rate policy,” Milei said. “But there are causes that rise above any political difference. The Malvinas is one of them.”

Some were skeptical.

“He wants to use the legitimate sovereignty claim over the Malvinas Islands to regain ground ahead of the election year and serve U.S. interests in its dispute with Britain,” said Nicolás del Caño, a leftist opposition lawmaker.

Argentina maintains that it inherited sovereignty over the islands from its former colonizer, Spain, and that Britain has illegally occupied them since 1833. Britain rejects that claim, citing the islanders’ desire to remain a British overseas territory.

For decades, successive U.S. administrations have remained neutral on the competing claims while recognizing Britain’s de facto administration of the islands. Any departure from that position would be a major diplomatic affront and inflame already high trans-Atlantic tensions.

On Monday, Trump stirred concern in Britain when asked whether his administration was reviewing its stance on the decades-old dispute. “I always review every position,” he replied. “That’s just one of many.”

Then, in an interview aired Thursday with British broadcaster GB News, Trump dodged directly answering a question about whether the U.S. would “come to the aid” of Britain in another conflict over the Falklands. Instead, he repeated past complaints that Britain had not provided sufficient support for the U.S.-led bombing campaign against Iran.

“Your country was not there to help me,” Trump said, recalling Britain’s former prime minister, Keir Starmer, telling him the country did not have ships to contribute to the campaign. “It was pretty sad, the whole thing.”

The Trump administration has floated the Falklands as leverage before: An internal Pentagon email leaked in April first raised the prospect of Washington reconsidering its position on the islands as one possible way to punish NATO allies that declined to join the U.S. war on Iran.

His comments forced Downing Street to insist that Britain would not yield sovereignty over the Falklands.

“Sovereignty rests with the U.K., and the islanders’ right to self-determination is paramount,” British Prime Minister Andy Burnham’s spokesman, Tom Wells, said earlier this week, pointing to a 2013 referendum in which the roughly 4,000 people living in the Falkland Islands voted overwhelmingly in favor of remaining a British overseas territory.

Under pressure from Argentina’s populist opposition, which accuses him of neglecting Argentina’s sovereignty claim, Milei has grown more vocal on the Falklands as plans for large-scale oil production around the islands raise the economic stakes of the dispute.

In his speech, Milei warned that the Sea Lion project could usher in a broader Falklands oil boom, enriching the islands with resources Argentina claims as its own and further entrenching Britain’s presence. There was no immediate response early Friday from Downing Street.

“If we allow it, we will be creating an incentive for the British government to deepen the occupation of the islands and the exploitation of our resources,” Milei said.

He vowed to fast-track sanctions against companies involved in oil projects around the islands and extend penalties to suppliers, shareholders and directors. His proposed legislation could also bar companies tied to such projects from operating or signing contracts in Argentina.

Despite slashing public spending elsewhere as part of his austerity drive, Milei also pledged more money to build a naval base in Tierra del Fuego and upgrade Argentina’s telecommunications capabilities there to strengthen the country’s presence in the South Atlantic.

“A poor country without armed forces can hardly make effective progress on its sovereignty claims,” he said.

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Associated Press writers Jill Lawless in London, Zeke Miller in Washington and Almudena Calatrava in Buenos Aires, Argentina, contributed to this report.