The COVAX global vaccine sharing scheme expects to deliver 35.3 million doses of AstraZeneca's Covid-19 vaccine to 36 Caribbean and Latin American states from mid-February to the end of June, the World Health Organization's regional office said.
The Pan American Health Organization (PAHO) said the Americas region needed to immunise about 500 million people to control the pandemic.
It said WHO would complete its review in a few days of the AstraZeneca vaccine for emergency use listing (EUL).
"The number of doses and delivery schedule are still subject to EUL and manufacturing production capacity," PAHO said, adding that supply deals also had to be agreed with producers.
Of the 36 nations receiving AstraZeneca's shot, it said four countries, namely Bolivia, Colombia, El Salvador and Peru, would also receive a total of 377,910 doses of the Pfizer and BioNTech vaccine from mid-February.
The GAVI alliance, the group that co-leads COVAX with WHO, said last week it aimed to deliver 2.3 billion vaccines worldwide by the end of 2021, including 1.8 billion free doses to lower-income countries.
Geneva-based GAVI was expected to publish details of its allocations by country on Monday.
The 36 Caribbean and Latin American nations to receive the AstraZeneca vaccine ranged from regional giants Brazil and Mexico to small islands such as Dominica and Montserrat.