The Trump administration banned cruises to Cuba under new restrictions on US travel to the Caribbean island imposed on Tuesday to pressure its government to reform.
The tightening of the decades-old US embargo on Cuba will further wound its economy, as well as hurt US travel companies that had built up Cuban business during the brief 2014-16 detente between the two countries.
The State Department said the US will no longer permit visits to Cuba via passenger and recreational vessels, including cruise ships and yachts, as well as private and corporate aircraft.
The US Commerce Department told Reuters the ban would be effective from Wednesday, giving cruise lines no grace period to change destinations and creating confusion among cruise passengers.
"Please tell me that my cruise to Cuba [in 18 days] is still going to be a cruise to Cuba," beseeched Matthew Watkins on Twitter.
Royal Caribbean Cruises announced that ships sailing Wednesday and Thursday would no longer stop in Cuba and it would provide updates on future cruise destinations.
Carnival Corp said it would have additional information in "the very near future." Norwegian Cruise Line likewise said it was monitoring the situation.
The US will also no longer allow so-called group people-to-people educational travel, one of the most popular exemptions to the overall ban on US tourism to Cuba. Travel experts said some groups may get around that by instead using one of the 11 other categories still allowed.
The administration of US President Donald Trump had announced the new restrictions in April as part of its rollback of the US-Cuban detente under former president Barack Obama and its broader battle against socialism in Latin America.
Cuba experts said the Trump administration appears to be partly eyeing the presidential elections next year, with the key swing state of Florida home to many Cuban-American exiles who welcome the harder line on Havana.
"The Administration has advanced the president's Cuba policy by ending 'veiled tourism' to Cuba and imposing restrictions on vessels," said a tweet from Trump's national security adviser John Bolton, who has led the US campaign against what he has called the "troika of tyranny" of Cuba, Venezuela and Nicaragua.
"We will continue to take actions to restrict the Cuban regime's access to US dollars."
Cuba's President Miguel Diaz-Canel said the island would not be intimidated.
"They have not been able to asphyxiate us, they will not be able to stop us, we will continue to live and we will conquer," he wrote on Twitter.
Many analysts have said the Trump administration is pursuing a failed policy of trying to overthrow Cuba's government through sanctions.
This is the second time the Trump administration has tightened US travel restrictions on Cuba. While the measures are designed to hit government coffers, they are also hurtingCuba's fledgling private sector, which the US has said it wants to support.
"This is another hard blow," said Miguel Ángel Morales, owner of La Moneda Cubana, a restaurant in Old Havana. "Around 50 percent of our business comes from the cruise ships."
