Tourists pass by images of US President Barack Obama and Cuban President Raul Castro in a banner that reads "Welcome to Cuba" at the entrance of a restaurant in downtown Havana, March 17, 2016. [Photo/Agencies]

Following is a chronology of how bilateral ties evolved since the two countries agreed in December, 2014 to restore diplomatic ties and end half a century of hostility following Cuba's revolution in 1959.

- Dec. 17, 2014
Obama and Cuban leader Raul Castro announced the start of the process to restore bilateral relations, after a telephone conversation two days earlier.

On the same day, the two countries agreed to prisoner exchange. Cuba released American contractor Alan Gross, jailed in Cuba for "contributing to domestic subversion," and the United States freed the three remaining members of the Cuban Five, intelligence agents arrested in Miami in 1998 on charges of spying.

- Jan. 15, 2015
The US Department of Treasury announced it would relax restrictions on exports, travel and currency exchanges with Cuba.

- Jan. 21, 2015
The first round of negotiations started in Havana between Cuba and the United States on the process of restoring diplomatic relations, migratory agreements and other bilateral issues of interest.

- Feb. 27, 2015
The second round of negotiations was held in Washington, aiming to discuss the restoration of bilateral ties and details for the reopening of embassies.

- March 16, 2015
The third round of negotiations kicked off as both countries agreed to maintain communication in the future as part of this process.

- April 11, 2015
Obama and Raul Castro officially met for the first time at the Summit of the Americas in Panama (they met informally and shook hands at Nelson Mandela's memorial in South Africa in December 2013).

- May 21, 2015
The fourth round of negotiations was held in Washington.

- May 29, 2015
Washington took Cuba off its list of countries that purportedly sponsor terrorism, which it issues annually.

- July 1, 2015
US and Cuba announced they will restore diplomatic relations and reopen their respective embassies.

- July 20, 2015
Cuba-US diplomatic ties officially restored after 54 years, six months and 17 days.

- Aug. 14, 2015
US Secretary of State John Kerry headed to Havana to preside over the raising of the US flag at the embassy, marking the first visit in seven decades by an official of his rank.

-- Sept. 11, 2015
The first meeting of the Cuba-US Bilateral Commission was held in Havana, charged with outlining the agenda of issues to be addressed as part of the process toward normalizing ties.

- Sept. 29, 2015
Castro and Obama met again at the headquarters of the United Nations (UN) in New York, during the 70th session of the UN General Assembly.

- Oct. 7, 2015
US Secretary of Commerce Penny Pritzker visited the island.

- Oct. 30, 2015
First Deputy Foreign Minister Marcelino Medina met in Havana with Alejandro Mayorkas, undersecretary of the US Department of Homeland Security.

- Nov. 2, 2015
Cuban state telecommunications company ETECSA signed an agreement with US company Sprint to provide direct roaming service to travelers to Cuba.

- Nov.9, 2015
The first meeting between Cuban and US law enforcement agencies was held in Washington, aiming to increase bilateral cooperation on security.

- Dec.1, 2015
Cuba and the United States held a technical meeting in Washington on cooperation in fighting drug trafficking.

- Dec. 11, 2015
Cuba and the United States agreed to re-establish direct mail service during a new round of talks in Miami.

- Dec. 16, 2015
The two countries agreed to resume regularly scheduled direct commercial flights.

- Feb. 4, 2016
Technical meeting was held in Miami between specialists from Cuba and the United States on fighting illegal immigration and trafficking.

- Feb. 16, 2016
Cuban Minister of Foreign Trade and Investment Rodrigo Malmierca headed a delegation to the second round of bilateral regulatory dialogue. It is the first visit by a Cuban official of such rank to Washington in half a century.

The two countries authorized no fewer than 110 regular daily flights from the United States to Cuba.

- Feb. 17, 2016
The US government authorized Alabama-based CleBer LLC to manufacture tractors in Cuba, making it the first US company to invest in the island since the 1959 Cuban Revolution.

- Feb. 18, 2016
Obama announced plans to travel to Cuba in March.

- Feb. 23, 2016
Technical meeting on cybersecurity was held in Havana between Cuban and US authorities, designed to boost bilateral cooperation in this area.

- March 14, 2016
Cuban telecom firm ETECSA and US Verizon Partner Solutions signed an interconnection accord that paves the way for direct telephone communication between the two countries.

- March 15, 2016
The US government announced new regulations to further increase trade and travel with Cuba, and lift financial restrictions on Cuba's use of the US dollar in certain transactions.

- March 16, 2016
Direct mail service between Cuba and the United States restored after nearly five decades.

- March 17, 2016
Cuba announced it will scrap a 10-percent tax on US dollars brought into the country.

- March 18, 2016
Cuban and US representatives in Havana signed a memorandum of understanding on cooperation in maritime navigation to improve safety.

- March 20, 2016
Barack Obama arrived in Cuba for an official visit that will end on Tuesday. He is the first US president to visit the island in 88 years.