A Cuban and American flag wave from the balcony of the Hotel Saratoga in Havana, Jan 19, 2015. [Photo/IC]

HAVANA/WASHINGTON - The United States and Cuba are set to announce the restoration of diplomatic relations on Wednesday.

The chief of the US interests section in Havana will report to Cuban foreign ministry around 9 am (1300 GMT) to deliver a letter from US President Barack Obama to Cuban President Raul Castro.

Obama will then speak at 11 am (1500 GMT) from the White House's ceremonial Rose Garden. It was unknown whether Castro would reciprocate with comments of his own.

Following 18 months of negotiations, the two leaders announced separately but simultaneously last December that they planned to reopen embassies in each other's capitals and normalize relations.

US Secretary of State John Kerry is expected at a flag-raising ceremony in Havana later this month, when the so-called US interests section will become a full embassy. Cuba's mission in Washington will undergo a similar upgrade.