President Barack Obama is flying to Cuba for a historic visit to the island and talks with its communist leader.
The two-day visit will be the first by a sitting US president since Calvin Coolidge went 88 years ago.
Mr Obama will meet President Raul Castro – but not retired revolutionary leader Fidel Castro – and the pair will discuss trade and political reform.
Protesters were arrested in the capital Havana just hours before Mr Obama was due to arrive.
Police took away dozens of demonstrators from the Ladies in White group, formed by wives of political prisoners, from outside a church where they attempt to hold weekly protests.
Correspondents say the visit marks a huge turnaround in US-Cuban relations.
It is hard to overstate the significance of this trip because as recently as 18 months ago, the idea of a US president setting foot on Cuban soil would have been unthinkable, the BBC’s North America editor Jon Sopel says.