(Updated and revised) A majority of Cuba-Americans, whose opposition to the Communist regime in Cuba helped cement a 50-year U.S. trade embargo, now support trade normalization of relations between the two countries, according to a poll that shows a significant shift in views since President Obama called for closer ties in December.

The survey of 400 Cuban-Americans by pollsters Bendixen & Amandi International, Miami, conducted in mid-March after the community had three months to debate and digest the new policy, showed 51 percent approved of Obama's call to end the embargo and improve trade relations, and 40 percent against. The poll claims a margin of error of 4.9 percent.

By contrast, a December poll taken in the two days following Obama's announcement showed only 44 percent of Cuban-Americans in favor of improved relations, with 48 percent against. The March numbers show a "significant shift," Fernand Amandi, principal at the polling firm, said in a statement announcing the poll at the Wharton Cuba Opportunity conference in New York today.

The pollsters found that Cuban-Americans in Florida, a center of opposition to the Castro regime, still opposed closer relations by a 49 percent to 41 percent margin. But Cuban-Americans in other states supported the new policy by a 3-to-1 margin: 69 percent to 23 percent. Younger Cuban-Americans, recent arrivals, and members of the community born in the U.S. were more pro-engagement than older Cuban-Americans and those born on the island.

"Industry in general favors lifting the embargo," and Cuban-Americans in business are starting to agree, said Frank Del Rio, chief executive of Norwegian Cruise Line Holdings Ltd., who left his native Cuba at age seven and hasn't yet been back. "My wife is also Cuban born. We have two children who have never been to Cuba. We have four grandchildren who we would like to see Cuba. It's just time. Some things in life you know it's the right time." He predicts Havana could rank with Nassau and Barcelona as a major world cruise port within two years of normalized relations.

The Wharton conference, co-chaired by sociologist Mauro Guillen, who runs Wharton's Lauder Institute, and Florida-based venture capitalist Faquiry Diaz Cala, assembled 250 investors, scholars and others interested in expanding Cuban-American cooperation.

Stefan Selig, undersecretary of the U.S. Department of Commerce, said the embargo represents a "failed policy," though it will take time for both countries to agree on major changes. He noted that European and Canadian investors have long been welcome to invest in Cuba, but few have done so on a large scale. The island's transport and communications infrastructure will need major upgrading first, he said.

Cubans can purchase mobile-phone service, but they have to pay in advance, and current U.S. rules make it difficult to transfer funds between Cubans and U.S. companies, Luis G. Coello, chief executive of Miami-based Cubamobile Communications, told me. He's hoping U.S. banking restrictions will ease soon, helping develop a broader market among Cubans hoping to finance mobile phone service.

Despite Obama's initiative, U.S. law still restricts U.S. investments in Cuba, and it's unclear whether Congress will ease restrictions anytime soon. Secretary of State John Kerry's staff has been negotiating the reopening of U.S. and Cuban embassies for the first time since 1961.

The Cuban government of Raul Castro has allowed more private restaurants and family hotels, but has resisted foreign ownershp and foreign-controlled hiring, and is encouraging the formation of cooperative enterprises that are less in contradiction with the ruling socialist ideology.

Whle the two sides have begun discussion on topics ranging from drug trafficking to healthcare investment, two of the most difficult issues -- the island's separate two separate currencies, for internal and trade use, and potential expropriation claims by U.S. companies and familes who fled the island -- may need to be resolved before U.S. investment becomes significant, Guillen told me.