The Obama administration’s loosening of travel and trade regulations to spur more exchanges with Cuba, while not fully lifting the congressionally imposed embargo, sought a form of American influence beyond the punishment of sanctions.

“The U.S. business community can help promote a more prosperous #Cuba that respects the universal rights of all its citizens,” Roberta S. Jacobson, the State Department’s top diplomat for the hemisphere, said on Twitter last week after attending a business conference in Manhattan. “It will be the people of #Cuba who drive reforms, which is why U.S. has taken steps to increase flow of resources, information to Cubans.”

But the euphoria that greeted news of the overture to Cuba in December has receded into a sobering reality of “coulds” — agriculture could be helped in a big way; companies could build hotels or resorts; credit cards could be used soon — that have yet to be realized in a significant way.

“How safe is it, business-wise, to do something in Cuba?” said an American lawyer who has been fielding a flood of inquiries from the private sector and spoke on the condition of anonymity to protect her business. “What if there is a change in administration in the U.S. in 2016? What happens now if capital goes in and there is a change on the part of Cuba? You never know if the Cubans are going to change their mind. I think there are a lot of unknowns because this is a whole new train.”

The lack of an American Embassy here and Cuba’s presence on a State Department roster of nations that sponsor terrorism have also scared off potential investors and left the Cubans, though suddenly not the pariah they once were in American business circles, reluctant to have serious discussions about the sort of business arrangements they have with foreign companies, mainly from Europe.

“Cuba feels, ‘I don’t want to start negotiating until I can trade with you,’ ” said Carlos Alzugaray, a former Cuban diplomat now living here.

“Most probably, we are at the stage where we are testing the water and seeing what there is,” he added. “We have to be careful with all these kinds of offers. A company might have a poor environmental record or a bad record of exploiting workers.”