Cuba will test its most advanced Covid vaccine candidate, in Iran, the research center that developed it announced on Saturday.

State-run Finlay Vaccine Institute (IFV) and the Pasteur Institute of Iran signed an agreement in Havana that will see a Phase 3 clinical trial in Iran, to “move forward faster in immunization against Covid-19 in both countries,” the IFV announced on Twitter.

The news came on the heels of Iran’s supreme leader on Friday banning the import of American and British-produced vaccines against Covid-19, saying they were “completely untrustworthy.”

Ayatollah Ali Khamenei said in a tweet, accompanied by the hashtag #CoronaVaccine: “It’s not unlikely they would want to contaminate other nations.”

The Islamic republic has reported more than 1.2 million cases of the novel coronavirus, which have caused over 56,000 deaths.

It has accused arch-enemy the United States of hampering its access to vaccines through a tough sanctions regime.

The Sovereign 02 is the country’s most advanced coronavirus vaccine candidate, showing “an early immune response (at 14 days),” IFV Director Vicente Verez said in December.

It has been difficult to do Phase 3 clinical testing in Cuba because its outbreak has not been as serious as those in many larger countries, he said.

Although cases in Cuba are increasing due to the opening of its borders, the country of 11.2 million has seen about 14,000 cases and 148 deaths, lower figures than its neighbors in the region.

The Americas’ only Communist-ruled state wants to have its entire population immunized with its own vaccines by the first half of 2021.

The Center for Genetic Engineering and Biotechnology is working on two other vaccine candidates, called Mambisa and Abdala. 

Cuban scientists have experience in developing and manufacturing vaccines. The national childhood vaccination program has 11 vaccines against 13 diseases, eight of which are manufactured on the island.