Donald Trump threatened on Monday to “terminate” the agreement restoring US relations with Cuba unless the communist island agrees to reopen and improve it.

“If Cuba is unwilling to make a better deal for the Cuban people, the Cuban/American people and the U.S. as a whole, I will terminate deal,” Trump tweeted.

The threat was welcomed by his biggest supporters.

“The Castro regime already broke the deal,” said John Bolton, a contender to be Trump’s next secretary of state, on Fox News.

“This is a potential hinge point in history,” he added, saying that Fidel Castro’s death is an “enormous political event” that could open Cuba to freedom and democracy in the future.

President Obama signed the agreement last year, smoothing relations between two nations that were severed after Castro seized control in 1959.

On Saturday, Obama issued a statement following Castro’s death saying that he “altered the course of individual lives, families and the Cuban nation.”

“History will record and judge the enormous impact of this singular figure on the people and world around him,” Obama said.

MSNBC reported Monday that many Cuban-Americans were “hurt and humiliated” by those comments, which failed to recognize that Castro was a dictator.

The White House announced Monday that neither the president nor the vice president would be attending Castro’s funeral.

Spokesman Josh Earnest said the official US delegation to the funeral has not been formed yet.

In contrast to Obama, Trump’s initial response was a blunt “Fidel Castro is dead!” tweet.

Trump aides later released a statement describing Cuba as a “totalitarian island” and said Castro’s legacy would include “firing squads, theft, unimaginable suffering, poverty and the denial of fundamental human rights.”

Some close to the president-elect’s transition team are not taking his Twitter threat to break relations with Cuba too seriously.

“I think Trump saw it as an easy way to score the Republican points,” one source said.

“Trying to read into Trump’s statements is fool’s errand,” the source added.