The Trump administration on Tuesday imposed major new travel restrictions on visits to Cuba by U.S. citizens, banning stops by cruise ships and ending a heavily used form of educational travel as it seeks to further isolate the communist government.

The Treasury Department said in a statement the U.S. will no longer allow the group educational and cultural trips known as “people to people” travel to the island. Those trips have been used by thousands of American citizens to visit the island even before the U.S. under Barack Obama’s government restored full diplomatic relations with the communist government in December 2014.

The new restrictions are part of a broader effort by the administration of President Donald Trump to roll back the Obama-era efforts to thaw relations between the United States and Cuba, which drew sharp criticism from the more hardline elements of the Cuban-American community and their allies in Congress.

Treasury Secretary Steven Mnuchin said the measures are a response to Cuba’s “destabilizing role” in the Western Hemisphere, including support for the government of President Nicolas Maduro in Venezuela.

“This administration has made a strategic decision to reverse the loosening of sanctions and other restrictions on the Cuban regime,” Mnuchin said. “These actions will help to keep U.S. dollars out of the hands of Cuban military, intelligence, and security services.”

Cruise ships in particular have brought thousands of Americans to Cuba and have provided an important economic lifeline to the island.

Cuban government figures show 142,721 Americans arrived on cruise ships between Jan. 1 and April 30, more than the 114,832 who came by plane. The figures exclude Cuban-born Americans visiting family on the island.

Cruise lines carrying passengers booked before Tuesday had been hoping that they could request specific federal permits to complete their trips to Cuba, said Pedro Freyre, a Miami-based attorney who represents Carnival and three other major cruise lines.

“For now, it’s prohibited unless the cruise lines requests a specific licence,” Freyre said. He said cruise lines had been trying to determine “if there’s any opening there to at least complete trips that have been booked and passengers that have made travel plans.”

Norwegian Cruise Line said in a statement that it was scrutinizing the new rules and consulting with lawyers and trade experts.

“We are closely monitoring these recent developments and any resulting impact to cruise travel to Cuba,” Norwegian Cruise Line said in a statement. “We will communicate to our guests and travel partners as additional information becomes available.”

Shore excursions from cruise ships tend to be organized by the cruise lines in co-operation with Cuban government tour agency Havanatur. A smaller number hire private tour guides or drivers of restored classic cars who wait outside Havana’s cruise docks.

“This affects all of us,” said William Martinez, 58, a Cuban-born American who lived in Florida for 46 years but returned five years ago to drive a classic car for tourists. “It’s inhuman, the sanctions that they’re putting on Cuba.”

Rubio praises latest move

Along with the cruise ships, the U.S. will also now ban most private planes and boats from stopping in the island.

“Consequently, private and corporate aircraft, cruise ships, sailboats, fishing boats, and other similar aircraft and vessels generally will be prohibited from going to Cuba,” according to the new rules published by the Commerce Department.

However, commercial airline flights appear to be unaffected, and travel for university groups, academic research, journalism and professional meetings will continue to be allowed.

“It kills the people-to-people category, which is the most common way for the average American to travel to Cuba,” said Collin Laverty, head of Cuba Educational Travel, one of the largest Cuba travel companies in the U.S.

The new restrictions had been previewed by national security adviser John Bolton in an April speech in Miami to veterans of the failed 1961 Bay of Pigs invasion, but details of the changes weren’t public until Tuesday.

Marco Rubio, the Florida senator born to Cuban émigré parents, praised the move as a “fulfilment” of Bolton’s promise and a repudiation of Cuba’s ties to Maduro.

The administration first began rolling back some of the Obama-era changes on travel in 2017.

The new restrictions take effect Wednesday, but the government will allow anyone who has already paid for a trip to go ahead with it.