Secretary of State John Kerry visited Cuba on Friday to raise the US flag over the newly reopened embassy, sealing Washington's historic rapprochement with Havana.
The Stars and Stripes have not flown over the glass-and-concrete building on the Havana waterfront since January 3, 1961, the day the United States severed ties with Cuba at the height of the Cold War.
And now US secretary of state has visited the island just across the Florida Straits since 1945.
"There will be hiccups along the way but it's a start," Kerry said of the nascent US-Cuban thaw, speaking to reporters traveling with him.
After touching down at Jose Marti International Airport, Kerry headed for the embassy, where he was due to preside over the flag-raising ceremony later Friday morning.
Accompanying him on the whirlwind one-day trip are three septuagenarian former Marines who lowered the flag for the last time 54 years ago.
The flag-raising ceremony will put a coda on the historic rapprochement announced on December 17 by US President Barack Obama and Cuban counterpart Raul Castro, which paved the way for the two countries to reopen their embassies on July 20.
Besides the key photo-op with the flag, Kerry will meet with Cuban officials, the head of the Catholic Church in Cuba and dissidents opposed to the communist regime.
He will not, however, meet with either Castro or his big brother Fidel, who led Cuba from its 1959 revolution until his retirement in 2006.
Underlining the sticking points still complicating relations between the two countries, Fidel Castro said in an essay published in Cuban state media Thursday -- his 89th birthday -- that the United States owes Cuba "many millions of dollars" because of the US trade embargo on the island.
He did not detail exactly how much money he believed was due, but Cuba said in September the half-century-old embargo had cost it $116 billion.
The United States for its part says Cuba owes $7 billion to American citizens and companies whose property was seized after Castro came to power.
The Castro government will use Kerry's visit to push for the lifting of the full embargo, in place since 1962.
Obama has called for an end to the embargo, but faces an uphill battle as he needs approval from Congress, where both houses are currently controlled by his Republican opponents -- many of them deeply hostile to communist Cuba.
Traveling with Kerry, Democratic Senator Patrick Leahy of Vermont said lifting the embargo was the fastest way to bring to change to Cuba.
"If we lift the embargo they won't be able to blame everything on us and I think change will come far more rapidly," he said.
In eight months of negotiations since the rapprochement was announced, the two sides have made progress on a number of other divisive issues, most notably the removal of Cuba from the United States' list of "state sponsors of terrorism."
But unresolved sources of tension include the US naval base in Guantanamo Bay and Cuba's treatment of the media, activists and dissidents.
The latter grabbed headlines last weekend when some 90 dissidents were arrested at a protest in Havana.
In a sign of the changing times, they were protesting not the Castro brothers but Obama, wearing sarcastic masks of the American leader to condemn the decision to reopen the embassy.
After counting Washington as their top ally for decades, opponents of the Castro regime are nervous the US-Cuban thaw will leave them out in the cold.
Kerry will be seeking to reassure them that the United States still backs their fight for democracy and human rights, while also trying not to step on the Cuban government's toes.
No Castro opponents have been invited to the flag-raising ceremony, which Kerry described as a "government-to-government" event.
But Kerry will speak with several dissidents during a private reception at the head of mission's residence later in the day, US officials said.
Kerry also plans to take a stroll through Old Havana and meet ordinary Cubans in the historic colonial district.