US Secretary of State John Kerry says the United States wants to be "good neighbours" to Cuba, but has cautioned the road to full relations remains "long and complex."
Speaking Spanish alongside his Cuban counterpart Bruno Rodriguez only hours after diplomatic ties were restored on Monday following a five-decade hiatus, Kerry said Washington "welcomes this new beginning in its relationship with the people and government of Cuba."
The secretary added "this milestone does not signify an end to the many differences that still separate our governments.
"But it does reflect the reality that the Cold War ended long ago, that the interests of both countries are better served by engagement than by estrangement," he insisted at a packed press conference at the State Department.
Those differences were immediately laid bare when Rodriguez swiftly demanded an end to the US economic blockade of the communist-run Caribbean island and the return of territory used as a US military base and jail in southern Guantanamo Bay.
"Totally lifting the blockade, the return of the illegally occupied territory of Guantanamo, as well as the full respect for Cuban sovereignty and the compensation to our people for human and economic damages, are crucial to be able to move towards the normalisation of relations," Rodriguez said.
Kerry said US President Barack Obama's administration wants to lift the economic embargo imposed on the communist-run Caribbean island in 1962, and he hoped it would be "soon."
The American diplomat, who met earlier with Rodriguez, stressed that "at this time, there is no intention to alter the existing lease treaty" on Guantanamo Bay, also home to a US military prison.
"But we understand that Cuba has strong feelings about it," Kerry said, as he confirmed he would visit Havana on August 14.
He will be the first US secretary of state to visit Cuba since 1945. And on a day of history, Rodriguez was the first Cuban foreign minister to be welcomed to the State Department since 1958.
"Make no mistake, the process of fully normalising relations between the United States and Cuba will be long and complex," Kerry cautioned, adding the US would not be "overflowing with expressions of optimism."
"Along the way, there are sure to be bumps in the road and moments of frustration. Patience will be required."
The Cuban flag was proudly flying over Havana's newly restored embassy in Washington on Monday for the first time in 54 years after the two bitter adversaries agreed in December to normalise ties.
The Cuban banner first took its place in the columned marble entrance hall to the State Department, hoisted before dawn between the flags of Croatia and Cyprus.
It was then raised at the Cuban embassy in Washington, which until Monday had been operating as an interests section.
It will not be raised at the newly-restored US embassy in Havana, however, until Kerry's visit next month.