US president Donald Trump has thrust America and Cuba back on a path towards open hostility with a blistering denunciation of the island's communist government.
He clamped down on some commerce and travel, but left intact many new avenues his predecessor Barack Obama had opened.
The Cuban government responded by rejecting what it called Mr Trump's "hostile rhetoric", but said it was willing to continue "respectful dialogue" on topics of mutual interest.
Even as Mr Trump predicted a quick end to President Raul Castro's regime, he challenged Cuba to negotiate better agreements for Americans, Cubans and those whose identities lie somewhere in between.
Diplomatic relations, restored only two years ago, will remain intact, but in a shift from Mr Obama's approach, Mr Trump said trade and other penalties would stay in place until a long list of prerequisites was met.
"America has rejected the Cuban people's oppressors," Mr Trump said in Miami's Little Havana, the cradle of Cuban-American resistance to Mr Castro's government.
"Officially, today, they are rejected."
Declaring Mr Obama's pact with Mr Castro a "completely one-sided deal", Mr Trump said he was cancelling it.
In practice, however, many recent changes to boost ties to Cuba will stay as they are.
Mr Trump cast that as a sign the US still wanted to engage with Cuba in hopes of forging "a much stronger and better path".
In a statement on government-run websites and television, President Castro's administration said Mr Trump's speech was "loaded with hostile rhetoric that recalls the times of open confrontation".
The lengthy statement then went on to strike a conciliatory tone, saying Cuba wants to continue negotiations with the US on a variety of subjects.
"The last two years have shown that the two countries can cooperate and co-exist in a civilised way," it said.
Embassies in Havana and Washington will remain open and US airlines and cruise ships will still be allowed to serve the island 90 miles south of Florida.
The "wet foot, dry foot" policy, which once let most Cuban migrants stay if they made it to US soil but was ended under Mr Obama, will remain so and remittances from people in America to Cubans will not be cut off.
But individual "people-to-people" trips by Americans to Cuba, allowed by Mr Obama for the first time in decades, will again be banned and the US government will police other trips to ensure travellers are pursuing a "full-time schedule of educational exchange activities".
The changes will not go into effect until new documents laying out details are issued.
Once implemented, Mr Trump's policy is expected to curtail US travel by creating a maze of rules for Americans to obey.
It bans most financial transactions with a yet-unreleased list of entities associated with Cuba's military and state security, including a conglomerate that dominates much of Havana's economy, such as hotels, state-run restaurants and tour buses.
Surrounded by Florida Republican officials, the president was unabashed about the political overtones of his election victory and Friday's announcement, saying: "You went out and you voted, and here I am, like I promised."
Cheered by Cuba hardliners in both parties, Mr Trump's new policy is broadly opposed by US businesses eager to invest in Cuba.
The US Chamber of Commerce, typically supportive of Republican presidents, predicted the changes would limit prospects for "positive change on the island" and Minnesota Republican congressman Tom Emmer, said the policy was "misguided" and would hurt the US economically.
Mr Trump's declaration in a crowded, sweltering auditorium was a direct rebuke to Mr Obama, for whom the diplomatic opening with Cuba was a central accomplishment of his presidency, yet it also exposed the shortcomings in the Obama approach.
Unable to persuade Congress to lift the decades-old trade embargo, Mr Obama had used his power to adjust the rules that implement the embargo to expand built-in loopholes.
Mr Obama and his aides argued that commerce and travel between the countries, which has blossomed since he relaxed the rules, would make his policy irreversible.
For Cubans, the shift risks stifling a nascent middle class that has started to rise as Americans have flocked to the island on airlines, patronising thousands of private bed-and-breakfasts.
"When he's cutting back on travel, he's hurting us, the Cuban entrepreneurs," said Camilo Diaz, a 44-year-old waiter in a restaurant in Havana.
"We're the ones who are hurt."