Havana - The United States and Cuba will hold their highest level talks in decades on Wednesday, ditching decades of Cold War-era hostility to pave the way to reopen embassies and normalise ties.Senior US and Cuban officials will meet over two days in Havana to discuss immigration issues and a roadmap to return ambassadors to each other's nation, more than half a century after full diplomatic relations broke off in 1961.The talks in the Cuban capital come five weeks after US President Barack Obama and Cuban counterpart Raul Castro simultaneously made the momentous announcement that their countries would seek to normalize ties.Roberta Jacobson, the US assistant secretary of state for Western Hemisphere affairs, will head the American delegation while the Cubans will be represented by the foreign ministry's director for US affairs, Josefina Vidal.As the two nations get closer, one person has been noticeably quiet and absent: The 88-year-old retired leader Fidel Castro has not reacted publicly to the rapprochement, sparking speculation about his health.'No sudden miracles'The first day of the talks will centre on migration -- an issue that has vexed both nations for decades, with Cubans hopping on rickety boats to traverse 145kg of shark-infested waters to reach Florida.Then on Thursday, the two sides will discuss the process to re-establish diplomatic relations and bring back their embassies."I think that Jacobson's visit is, without a doubt, historic and it will bring changes, but it's important to be aware that you can't expect sudden miracles," said Peter Schechter, Latin America analyst at the Atlantic Council, a US think tank.Cubans have voiced hope that the warming ties will translate into improvements in their daily lives in a country where supermarket shelves are bare and people make around $20 a month.In the United States, most Americans approved Obama's move, with a survey released Friday showing that two-thirds favour lifting the embargo.But some lawmakers on both sides of the partisan divide have criticised Obama's decision, with Republican Senator Marco Rubio, a Cuban-American, saying the White House had "conceded everything and gained little" from the Castro regime.The Obama administration already took a major step on Friday when it used executive powers to loosen some travel and trade restrictions.While the move will allow more Americans to visit Cuba and do business with the communist country, the US Congress still has the final say on ending a five-decade-old embargo that has forbidden most commerce and general tourism.For its part, the Cuban government completed this month the release of 53 political prisoners who were on a list provided by the United States.Terror sponsor listAnalysts say this week's talks will allow the two countries to make progress in preparations to reopen embassies. The two countries are currently represented by "interests sections" without ambassadors.For Cuba, a crucial part of the negotiations will be getting its name out of a US blacklist of nations that sponsor terrorism, which has prevented the government from qualifying for credit from international financial institutions."This is not something small, because staying on the list bars access from financial institutions," Schechter said."The talks should initially focus on the most pressing questions to establish diplomatic relations, in order to then move to central issues," he said.Those issues, he said, include concerns over individual liberties; the status of the US naval base at Guantanamo Bay in eastern Cuba, and compensation for properties that were nationalised after Fidel Castro's revolution in 1959.The talks will be held in Havana's Convention Centre, where Cuba has been hosting peace talks between the Colombian government and the Marxist Farc guerrilla movement.Jacobson will leave Cuba on Friday after meeting with dissidents, who have shown concern about the policy shift of the United States, which has been their main ally and source of funding over the years.Her visit comes after six US lawmakers, led by Democratic senator Patrick Leahy, close on Monday a two-day visit to the island. The legislators met with dissidents on Sunday.