The announcement, by Chinese foreign minister Wang Yi, followed a virtual meeting with his counterparts on Wednesday.
In a statement the Mexican government said: "China's foreign minister said that the vaccine developed in his country will be a public benefit of universal access, and that his country will designate a loan of $1bn to support access for the nations of the region."
Apart from Mexico, foreign ministers from countries including Argentina, Barbados, Chile, Colombia, Costa Rica, Cuba, the Dominican Republic, Ecuador, Panama, Peru, Trinidad and Tobago and Uruguay were on the call.
Chinese biotech company Sinovac has begun a phase three vaccine trial in Brazil. Another phase three trial is being carried out by Oxford University and AstraZeneca.
Brazil has the second highest number of confirmed coronavirus cases in the world, with 2,287,475 as of Saturday morning, according to a tally by Johns Hopkins University. Only the US has a higher number, with 4,130,783.
Along with India, Russia and South Africa, Latin American countries are among the worst affected: Mexico has 378,285 cases, Peru has 375,961 and Chile 341,304.
China has been loaning hundreds of billions of dollars to poorer countries as part of its so-called Belt and Road initiative which is designed to extend its global influence. Most of the money is destined for infrastructure projects like ports, roads and railways.
Last month Beijing said about a fifth of its lending under the initiative had been affected by the economic fallout from the coronavirus pandemic.
Reuters contributed to this report
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