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The highest-ranking U.S. diplomat to travel to Cuba in nearly 40 years boarded a commercial flight Wednesday morning from Miami — ahead of negotiations to re-establish diplomatic ties between the two countries.

Roberta Jacobson, assistant secretary of state for Western Hemisphere affairs, is leading the delegation in Havana and will be focusing on President Barack Obama's initiative to open respective embassies in both capitals. In addition, the talks through Friday would set the stage in the next few months for a trip by Secretary of State John Kerry.

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The agreements would ultimately lift trade and economic sanctions after decades of Cold War-era hostilities between the U.S. and Cuba. Both countries are envisioning regularly scheduled commercial flights, banking and credit, mail service and expanded travel, officials have said. The White House also hopes that Cuba will permit Internet companies to create service accessible across the island.

As Jacobson arrives in Havana, a congressional delegation led by Sen. Patrick Leahy, D-Vt., an advocate of normalizing relations, returned Monday night from the communist island. Leahy told MSNBC on Tuesday that it could take a year or longer for some of the proposed changes to be realized.

Cuban officials, meanwhile, have warned the U.S. not to try and meddle in its communist ideologies — a point of contention from U.S. lawmakers who oppose the Castro regime. Obama during his State of the Union address on Tuesday night instead focused on the thawing of relations — a plan that was reportedly in the works over the last 18 months and was announced last month in a surprise move. "In Cuba, we are ending a policy that was long past its expiration date," Obama said Tuesday. "When what you're doing doesn't work for 50 years, it's time to try something new."

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Details of the agenda for my meetings with the govt. of #Cuba and civil society Jan. 21-24. http://t.co/d5Aw8OeuUH — Roberta Jacobson (@WHAAsstSecty) January 20, 2015

During my trip to #Cuba I will discuss re-establishment of diplomatic relations: http://t.co/d5Aw8OeuUH — Roberta Jacobson (@WHAAsstSecty) January 21, 2015

— Andrea Mitchell and Erik Ortiz