President Trump cracked down Wednesday on U.S. travel and business with Cuba, a major step toward rolling back another Obama-era policy.

Under new regulations that take effect Thursday, the Trump administration is banning U.S. citizens from doing business with dozens of entities that have links to Cuba’s military, intelligence and security agencies.

The list includes stores, hotels, tourist agencies and even two rum makers frequently visited by Americans who have flocked to the communist country in recent years.

The Obama administration ended more than 50 years of diplomatic isolation with its Cold War foe in December 2014. The historic move re-established embassies in Havana and Washington, made it easier for Americans to visit the long-isolated island and was punctuated by a personal visit to Havana where President Barack Obama met several times with Cuban President Raúl Castro.

Trump repeatedly questioned this easing of hostilities. He vowed to cut the opening throughout the presidential campaign and claimed in June that the U.S. gave away too much in exchange for too little.

The White House also blamed Cuba for a series of unexplained attacks against U.S. diplomats on the island, prompting the State Department to cut back its staff in Havana and halt the processing of visas for Cubans trying to reach the United States.

On Wednesday, the Commerce, Treasury and State departments announced regulatory changes that will close many doors opened by Obama nearly three years ago. The administration says blocking Americans from providing money to Cuban businesses run by the military will drive visitors to support Cuba's growing class of private entrepreneurs, who run their own hotels, restaurants, taxis and small stores.

"We have strengthened our Cuba policies to channel economic activity away from the Cuban military and to encourage the government to move toward greater political and economic freedom for the Cuban people," Treasury Secretary Steven Mnuchin said.

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Among the changes being made:

• End 'people-to-people' visas

One of the biggest changes is to restrict "people-to-people" visas that thousands of Americans have used in recent years to travel to Cuba. The U.S. maintains an economic embargo against Cuba that prohibits travel there solely for tourism. Congress allows for Americans to travel only through certain visa categories, including religious, humanitarian, journalistic, diplomatic and business trips.

The Obama administration expanded those categories, allowing U.S. travelers for the first time to book a flight online to Havana, buy a people-to-people visa at the counter of a U.S. airport and then go on their trip.

Now, those travelers will need to be accompanied by a U.S.-based tour guide who must ensure they are engaging in approved activities that help the Cuban people.

• Restrict educational visas

The new regulations also restrict Americans traveling to Cuba on educational visas, requiring traveling as part of a larger group overseen by a U.S.-based company.

• Bar certain hotels and rum factories

Approved travelers will also have fewer places to frequent in Cuba. The administration released a list of hotels, marinas, stores and rum factories owned by the Cuban military that will now be off-limits to Americans. The list includes 84 hotels: 27 in the capital Havana, 13 in the popular beach resort of Varadero and others spread around the island.

The list even includes the Hotel Ambos Mundos, a favorite of American author Ernest Hemingway.

Sen. Bob Menendez, D-N.J., along with other Cuban-American members of Congress who opposed opening relations with Cuba, described the changes as "a step in the right direction."

Rep. Mario Diaz-Balart, R-Fla., said the new regulations did not go far enough to cut off U.S. monetary assistance to Cuba’s ruling class.

"It is clear that individuals within the bureaucracy who support the former administration's Cuba policy continue to undermine President Trump," Diaz-Balart said. "I look forward to working with the president to ensure that his policy is fully implemented."

Supporters of Obama's renewed diplomatic ties with Cuba criticized Trump's new changes. Sen. Patrick Leahy, D-Vt., said the move will hurt the island's burgeoning class of private entrepreneurs, because Americans will now be more hesitant to make the trip.

"These new regulations are reminiscent of the Cold War and what one would expect of a paranoid totalitarian government, not a democracy like ours," Leahy said in a statement.

Josefina Vidal, chief of U.S. affairs for Cuba’s Ministry of Foreign Affairs, questioned the validity of the “arbitrary” list of restricted businesses announced on Wednesday. She said the new regulations represented a “regress of bilateral relations” that will hurt the Cuban people, U.S. citizens who cannot freely travel, and U.S. businesses interested in dealing with Cuba.

“Some of the measures do not conceal their subversive undertone, like the one urging travelers to engage in activities of this sort to justify the legality of their visits to Cuba,” Vidal said in a statement.

Engage Cuba, a coalition of companies that supported Obama's opening, said pulling more Americans out of Cuba will only increase the influence of Russia, which has been re-establishing itself on the island.

"It seems we have fumbled our Cuba policy right into the hands of (Russian President) Vladimir Putin," said James Williams, president of Engage Cuba.

Others pointed to the timing, as Trump travels through Asia.

"At a time (when) President Trump is meeting with Communist leaders in China and Vietnam, these regulations show the absolute hypocrisy and political pandering of the Trump administration on Cuba,” said Collin Laverty, president of Cuba Educational Travel, a group that arranges trips for Americans to Cuba. “They serve to placate a fading minority in South Florida, harming American and Cuban workers and families."

The practical effect of the changes for U.S. businesses represents a slowdown, but not a complete shutdown of their efforts in Cuba, according to Pedro Freyre, an attorney with the Akerman law firm in Miami who represents JetBlue, Carnival Cruise Line and other companies operating in Cuba.

Freyre said U.S. businesses working in Cuba’s tourism industry will take a hit. But he pointed out that many aspects of Obama’s opening — direct flights from U.S. cities, U.S.-flagged cruise ships traveling to Cuba, diplomatic relations— were not eliminated as many feared.

Instead, the Trump administration banned U.S. companies with dozens of Cuban companies that were never even considered by Americans, such as Cuba’s national police, the investigative arm of Cuba’s Navy and Cuba’s border patrol agents.

“Initially there’s going to be a chilling effect: ‘Oh my God, there are all these new restrictions,’” Freyre said. “But it’s a relatively limited restriction. It will limit trade somewhat, but it will not stop it.”

The new regulations do no affect the ability of U.S. citizens to buy Cuban rum and cigars and bring them back home.