American businesses that have ventured into Cuba since former President Barack Obama moved to normalize relations with the country more than two years ago may see some of their progress thwarted by President Donald Trump's revision of Obama's policy.

Trump announced in Miami on Friday plans to tighten restrictions on American travel to Cuba and clamp down on U.S. business dealings with the Cuban military and intelligence security services. He has instructed the Treasury and Commerce Departments to begin writing new regulations on Cuba in a maneuver to reverse the efforts Obama took in late 2014 to ease the more than 50-year embargo against the island.

"A free Cuba is what we will soon achieve," he told a crowd of onlookers on Friday. "I keep my promises. Sometimes in politics they take a little bit longer... but we get there."

Trump's aim is to restrict the flow of money to oppressive elements of the Cuban regime and ensure that the statutory ban on tourism is strictly enforced. His policy reaffirms the U.S. statutory embargo on Cuba and opposes calls in the United Nations for its termination. It also mandates regular reporting on Cuba's progress.

Trump will not close embassies, break diplomatic relations or cut off commercial flights between the U.S. and Cuba, nor will he bring back the "wet foot, dry foot" policy toward Cuban immigrants eliminated by Obama in January.

The Treasury Department on Friday issued a Q&A on the changes.

Proponents of opening the U.S. to Cuba warned that Trump's overhaul will be a setback in an already slow-moving process and could harm American businesses that have entered the country under Obama. U.S. business have established 26 agreements with the Cuban government since 2015, according to ABC News.

"There are currently many different business sectors exploring options to expand their footprint in Cuba, and others have signed deals," said Alana Tummino, senior director of policy and head of the Cuba Working Group at the Americas Society and Council of the Americas (AS/COA).

"Cuba, even before the changes [under Trump]...was still one of the most highly complicated and sanctioned countries in the world from the United States, so businesses were already at a deep, deep disadvantage of entering into the Cuban market," said James Williams, president of Engage Cuba, a group that advocates for lifting the U.S. trade embargo. "Over the last two years, we've finally seen the fruits of those efforts starting to produce results."

Tourism companies have the most to lose from Trump's new Cuba policy, which will restrict self-directed travel and instead push American travelers into group trips that allow the U.S. government to ensure they are engaging in educational and cultural exchanges and not pure tourism. Group trips are more expensive than individual ones and will likely result in curbed travel.

A number of airlines have taken advantage of relaxed travel restrictions to Cuba under Obama, including American Airlines (AAL) - Get Report , Delta Air Lines (DAL) - Get Report , JetBlue (JBLU) - Get Report , Southwest (LUV) - Get Report and United Continental (UAL) - Get Report . Cruise operators Royal Caribbean (RCL) - Get Report , Carnival (CCL) - Get Report and Norwegian Cruise Line (NCLH) - Get Report have benefited as well.

To be sure, it has not been as fruitful as many had hoped. Some airlines that sought business in Cuba have since reversed course, including Frontier Airlines and Silver Airways, which dropped services entirely, according to Bloomberg.

Editors' pick: Originally published June 16.

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Starwood Hotels & Resorts (HOT) last year opened the first Cuban hotel managed by a U.S. company in more than 50 years. Airbnb opened up its platform to Cuba in 2015 and has since seen 22,000 listings.

Telecommunications and remittance companies have ventured into Cuba as well. T-Mobile (TMUS) - Get Report , Sprint (S) - Get Report , Verizon (VZ) - Get Report and AT&T (T) - Get Report have reached roaming agreements there, and Google (GOOGL) - Get Reportinked a deal with state-run ETECSA to speed up services there in December. Western Union (WU) - Get Report allows remittances there.

It's not yet clear how damaging Trump's revised policy will be to non-travel companies.

"The devil will be in the details," Williams said. "How Commerce and Treasury write regulations will decide how significant the impact will be on U.S. business."

"Any change in regulations in Cuba policy takes time. We saw with the previous administration the very deliberate work they did to communicate and learn from U.S. companies to understand the kinds of obstacles they faced from a U.S. regulatory perspective and bringing their services to the island," said Tummino. "We'll see if these regulatory agencies take the same approach."

An administration official said the new policy "does not target the Cuban people, but it does target the repressive members of the Cuban military government" by attempting to cut off commerce with Cuban military and intelligence services. But the Cuban government will likely be able to find a way around restrictions.

"They would just find a way to transfer the ownership rights from the holding company that is currently now controlled by the military and simply transfer those rights to another state-owned entity that might be controlled by the ministry of tourism or the economy," said Gustavo Arnavat, senior adviser at the Center for Strategic and International Studies and former Obama administration appointee to the Inter-American Development Bank.

Cuba hawks Senator Marco Rubio (R-FL) and Representative Mario Diaz-Balart (R-FL) are among Trump's biggest cheerleaders on reversing Obama Cuba policy, but there are some indicators they might not be getting all that they want -- specifically, rum and cigars.

The Cuban government runs cigar-making and Cuban-distilled Havana Club rum. When a reporter on Thursday asked whether Trump intended to change the Obama administration's lifting of restrictions on Americans bringing back rum and cigars, a senior White House official indicated the Obama policy would be untouched. "There aren't any changes to the regulations on what items Americans can bring back from Cuba," the official said.

If Trump's new policy were especially harsh, he wouldn't allow such souvenirs.

"If this policy will allow U.S. companies to do business with Cuban state-owned enterprises that are not military-controlled, then this is not such a big deal," Arnavat says.

Still, for American businesses testing the water in Cuba, Trump's reversal of some of Obama's orders is less than ideal.

"Even while it's true that Cuba is not China, it does represent a new market for American firms to take advantage of," Arnavat said.

"There's no way to see this as anything but a step back," said Williams.

Editors' pick: Originally published June 16.

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