US Interests Section chief Jeffrey DeLaurentis on Wednesday delivered a letter from President Barack Obama to Cuba’s President Raul Castro on re-establishing diplomatic relations and opening embassies.
De Laurentis was received by acting Foreign Minister Marcelino Medina, Spanish news agency Efe reported.
It is expected that the historic announcement on re-establishment of the embassies in Washington and Havana will be made in the next few hours.
Earlier, CNN quoted a White House official as saying that in Havana, the American embassy is likely to occupy the same building where the Interests Section currently operates.
That is the same structure, situated on the Havana waterfront, which housed the American embassy prior to the severing of diplomatic ties after the Cuban Revolution in the 1950s.
"We expect President Barack Obama and Secretary John Kerry to address this publicly tomorrow morning," the official added.
The re-establishing of embassies is a final step in the full diplomatic thaw President Obama initiated in December.
Since then, the US has eased some travel restrictions to Cuba and allowed for some new economic ties.
In April, Obama met President Castro during a summit meeting in Panama, the first time the leaders of Cuba and the US had met in over 50 years.
The US officially removed Cuba from its list of state sponsors of terror earlier in June.