Backgrounder: A chronology of improved ties between Cuba, U.S.

U.S. President Barack Obama arrived on Sunday in Cuba, in a historic visit that could mark the beginning of a new era in U.S. relations with its neighbor after more than 50 years of Cold War-era animosity.

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 U.S. 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

U.S. and Cuba announced they will restore diplomatic relations and reopen their respective embassies.

-- July 20, 2015

Cuba-U.S. diplomatic ties officially restored after 54 years, six months and 17 days.

-- Aug. 14, 2015

U.S. Secretary of State John Kerry headed to Havana to preside over the raising of the U.S. 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-U.S. 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

U.S. 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 U.S. Department of Homeland Security.

-- Nov. 2, 2015

Cuban state telecommunications company ETECSA signed an agreement with U.S. company Sprint to provide direct roaming service to travelers to Cuba.

-- Nov.9, 2015

The first meeting between Cuban and U.S. 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 U.S. government authorized Alabama-based CleBer LLC to manufacture tractors in Cuba, making it the first U.S. 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 U.S. authorities, designed to boost bilateral cooperation in this area.

-- March 14, 2016

Cuban telecom firm ETECSA and U.S. Verizon Partner Solutions signed an interconnection accord that paves the way for direct telephone communication between the two countries.

-- March 15, 2016

The U.S. government announced new regulations to further increase trade and travel with Cuba, and lift financial restrictions on Cuba's use of the U.S. 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 U.S. dollars brought into the country.

-- March 18, 2016

Cuban and U.S. 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 U.S. president to visit the island in 88 years. Enditem