The U.S. is one step closer to having an army of genetically-modified mosquitoes that fight Zika through breeding.

The U.S. Food and Drug Administration has given the go-ahead on a field trial for the Oxitec mosquito in Key Haven, Monroe County, Florida. The agency on Friday released a "Finding of No Significant Impact" and "Final Environmental Assessment," the last step the mosquito's maker, the U.K.-based Oxitec, needs to take with the agency.

Oxitec will wait for a local non-binding referendum on the field trial in November before begins its trial with the Florida Keys Mosquito Control District. The company is a subsidiary of Intrexon.

The plan is to release genetically engineered mosquitoes into areas where the Aedes aegypti mosquito species is known to live.

The Oxitec mosquito contains a "self-limiting" gene that causes any offspring it has to die. Oxitec releases genetically engineered male mosquitoes — which don't bite — into the wild to mate with wild female Aedes aegypti mosquitoes, they breed, and the offspring die before reaching adulthood.

In addition to Zika, Aedes aegypti is a vector for many diseases, including yellow fever virus, dengue virus and chikungunya virus.

The company is able to breed the mosquitoes by giving them an antidote to the self-limiting gene that is not present in the wild.

The disease has been spreading rapidly throughout Central and South American countries, such as Brazil and the U.S. territory Puerto Rico.

This week, the state of Florida identified a small but growing number of cases of the virus transmitted from local mosquitoes, and has asked for assistance from the U.S. Centers for Disease Control and Prevention.