The baby banteng - a type of wild cattle found in south-east Asia - was born a week ago and appears to be normal.
The scientists involved say it proves that cloning does have a part to play in preserving species which may soon be extinct.
But others are still highly dubious, arguing that preservation of diminishing habitats would be a more effective way to approach the problem.
'Surrogate mothers'
Scientists from Advanced Cell Technology, in Worcester, Massachusetts, US, created the clone using DNA from frozen banteng cells kept by San Diego Wild Animal Park.
The researchers inserted this DNA into eggs from ordinary domestic cows, and also used cows as "surrogate mothers" to carry the embryos to term.
From 30 embryos created, two calves were born. One was abnormal and was put down, but the scientists in charge say the other seems to be thriving.
This is not the first attempt to clone endangered animals using domestic species. Two years ago a gaur, a type of wild ox, was cloned by ACT, but it died within a couple of days.
More success was had by an Italian-led team which produced a "healthy" clone of the European mouflon lamb, a rare breed of sheep found on Sardinia, Corsica and Cyprus.
Others to follow
The International Union for the Conservation of Nature (IUCN) lists the banteng (Bos javanicus) as "severely threatened".
The white-stockinged animal has been hunted for its slender, curved horns. Only four to eight thousand now remain in south-east Asia; 20 years ago, there were around five times that number.
Most of the living animals are found on the island of Java.
The researchers say their creation proves that cloning can help endangered species; but the real test will come in about six years' time, when the cloned banteng reaches sexual maturity and is ready to breed.
If it can produce offspring, that will give hope to other researchers who want to use cloning to preserve animals as diverse as the panda and the wild cat.
Difficult and expensive
If it survives, the remaining banteng will be transferred to the San Diego Wild Animal Park and encouraged to breed.
"The fact that it can happen at all just astounds me," Oliver Ryder, a geneticist at the San Diego Zoo's Center for Reproduction of Endangered Species, told Reuters.
In 1977, the zoo began preserving cells and genetic material from hundred of animals in a program it dubbed the Frozen Zoo. Tissue samples from each animal are stored in small plastic vials, which are submerged and frozen in liquid nitrogen.
"At the time we did not know how this resource might be used, but we knew it was important to save as much information about endangered species as we could," Ryder said.
Many conservationists are sceptical about the value of cloning in helping to save endangered animals.
They argue there is little point pursuing this difficult and expensive technology if the reasons for an animals' decline or disappearance, such as habitat loss, are not addressed first.
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