The Post's Katie Zezima breaks down the practical implications of the new U.S. policy toward Cuba, including travel, trade and bringing back Cuban rum and cigars. (Jorge Ribas/The Washington Post)

In the wake of President Obama’s historic decision to mend diplomatic ties with Cuba, U.S. businesses and potential tourists scrambled to figure out what new opportunities will be available on the island and to position themselves at the head of the line.

The political conversation sparked by Obama’s Wednesday announcement grew in both volume and dogmatism. Some hailed the opening as the dawn of pragmatic diplomacy. Others denounced it as a presidential sellout.

In news conferences and briefings, the administration provided details of what the new policy means. Trade and tourism will expand, as soon as new regulations can be published in the Federal Register, but the half-century trade embargo will continue to limit both unless Congress decides to lift it.

Reestablishment of formal diplomatic relations, while approved by both countries, requires a formal process that will begin with the visit to Havana next month of Assistant Secretary of State Roberta Jacobson, who is heading the U.S. delegation for previously scheduled talks on migration.

Those talks, begun in 1995, take place every six months. This time, however, they will be used to start the normalization process, Jacobson said Thursday. It requires an exchange of diplomatic letters, and formal notification to the Swiss government, which has overseen U.S. affairs in Cuba for the past 53 years, that its services are no longer needed.

Then, Jacobson said, “we would change the sign” on the existing U.S. Interests Section on the Havana waterfront and open for business.

But in many ways, a new sign on the embassy and pending regulatory changes will be less a wholesale transformation in relations than they are an expansion of small measures that have been put in place gradually over the years.

The building that will become the U.S. Embassy served as the embassy for years before relations were severed, in 1961. Shuttered and abandoned, it was reopened in 1977 — with 16-year-old calendars and portraits of John F. Kennedy still on the wall — when then-President Jimmy Carter negotiated the establishment of Interest Sections with Cuba.

Since then, U.S. business in Cuba has been conducted by U.S. diplomats technically under the auspices of the Swiss Embassy, which has also overseen operations of the Cuban Interests Section in Washington. That building, on 16th Street NW, also served as Cuba’s pre-revolution embassy.

Amid the often-torturous ups and downs of estrangement, the interests sections have provided consular services, hosted meetings such as migration talks, promoted their country’s interests and provided services to their visiting citizens, and reported back to their capitals.

More than a decade ago, after years of limited telephone calls across the 90-mile Straits of Florida that often had to be booked days in advance, direct dialing was put in place. While still severely limited, Cubans can use the Internet.

The George W. Bush administration reduced trade sanctions — allowing export to Cuba of agricultural and medical goods under certain conditions — but tightened visits and remittances to the island. Obama expanded U.S. visits to Cuba and the number of American visas given to Cubans.

A difficult history between U.S. and Cuba
More than 50 years after the U.S.-imposed embargo, President Obama has announced an effort to normalize ties with Cuba.

(Kennedy Elliott, Julie Tate and Swati Sharma/Staff reports)

So far this year, more than 20,000 Cubans have received visas to migrate to this country, under a quota agreed on years ago, and an additional 35,000 non-immigrant visas have been issued. While Cuba has formally done away with exit visas, “more than we would like to see” are still prohibited from leaving, Jacobson said.

But the area surrounding the mission in Havana, prominent real estate along the Malecon waterfront, is now occupied by private shops offering visa photos and copying services. The U.S. Interests Section in Cuba is among the largest American diplomatic facilities in the region, and, by some reckonings, larger than any real embassy in Havana.

Sen. Marco Rubio (R-Fla.), who disapproves of the thaw with Cuba, has said that he would try to block funds for the embassy and oppose any Obama nominee for U.S. ambassador.

“I don’t think that that necessarily is one of the first things that we’ll get to,” Jacobson said of an ambassadorial appointment. Jeffrey DeLaurentis, the career Foreign Service officer who serves as chief of the Interests Section, will probably become charge d’affaires. Cubans already call him ambassador.

The regular, thousands-strong marches past the Havana mission ended years ago, and the Americans have stopped broadcasting provocative news flashes on the ticker outside the building.

Many restrictions remain. U.S. diplomats in the Cuban capital are prohibited from traveling outside Havana province, and their comings and goings — as well as those of their visitors — remain closely watched. In Washington, Cuban diplomats are banned from travel outside the Beltway.

In the future, Jacobson said, “we want [diplomats] to have the full range of privileges” under the Vienna Convention that governs diplomatic activities around the world. That includes, she said, “being able to talk to lots of different people in society.”

Beyond the White House — where his fellow National Security Council senior directors broke into spontaneous applause Thursday for Ricardo Zuniga, who played a key role during 18 months of secret talks with the Cubans — officials at the Commerce and Treasury departments toiled over new regulations that would govern issues such as how Cuba will pay for newly allowed U.S. imports, how much money Cuban Americans can send to their families, which Americans can go to Cuba as tourists and how many cigars they can bring back with them.

Asked when the regulations would be published, Jacobson said, “I am quite certain we’re talking about days or weeks. Certainly not months.”

It remains to be seen whether the tightly controlled Cuban government and economy will allow citizens to take advantage of the loosening restrictions from the U.S. side. While the embargo on most goods continues, Obama has said he will ease restrictions on items such as telecommunications equipment, for example, which will allow more Internet access.

“There are other things that need to be agreed upon that have always been part of the discussion of diplomatic relations with Cuba,” Jacobson said, including thousands of claims that have been registered against the Cuban government in U.S. courts, most involving property confiscated from Cuban nationals — many of whom are now U.S. citizens — by the revolutionary government, and a Cuban lawsuit against the United States.

“We do not believe those things would be resolved before diplomatic relations would be restored,” she said. “but we do believe that they would be part of the conversation. . . . There’s no real timeline of knowing when each part of it will be completed, because it has to be completed by agreement of both governments.”

Jacobson said that the State Department has already begun the process of reviewing Cuba’s presence on its list of state sponsors of terrorism. Removal from the list, which Jacobson said is not assured, requires a lengthy process to determine that Cuba has not participated in or supported acts of international terrorism over the past six months, has renounced the use of terrorism and ratified international treaties against terrorism.

But the list itself is somewhat subjective, as evidenced by North Korea’s removal from it in 2012. In addition to Cuba, Iran, Sudan and Syria are on the list. The United States has diplomatic relations with Sudan, and relations with Syria are suspended but not broken.

Nick Miroff in San Diego contributed to this report.