A southern white rhino at a California zoo has been impregnated through artificial insemination, researchers announced on Thursday, in what could prove a major step in saving a nearly extinct close relative.

The rhino called Victoria was inseminated in March at the San Diego Zoo and the embryo will continue developing for about 14 months, meaning that the calf would be born in summer 2019.

"The pregnancy, created through artificial insemination with sperm from a male southern white rhino, is an important milestone in the ongoing work to develop the scientific knowledge required to genetically recover the northern white rhino, a distant subspecies of the southern white rhino," officials at the San Diego Institute for Conservation Research said in a statement.

"Only two northern white rhinos currently remain on Earth (unfortunately both are female)," the statement added.

Barbara Durrant, the director of reproductive sciences at the institute, said that while news of the pregnancy was something to celebrate, it was still too early to determine whether it would lead to the birth of a healthy rhino.

Artificial insemination of rhinos has rarely been attempted in zoos and there have only been a few births from this procedure in the past, the institute said.

The northern white rhino on the brink of extinction Adrian Leung, AFP

It added that to reach the ultimate goal of successfully producing a northern white rhino, multiple steps must be accomplished.

"One of the first steps involves sequencing the genome of the northern white rhino to clarify the extent of genetic divergence from its closest relative, the southern white rhino," the statement said.

Another step, it added, requires conversion of cells preserved from 12 individual northern white rhinos to stem cells that could develop into sperm and eggs.

"There are many challenges ahead, but researchers are optimistic that a northern white rhino calf could be born from these processes within 10 to 15 years," the institute said. "This work also may be applied to other rhino species, including critically endangered Sumatran and Javan rhinos."

Sudan, the last male northern rhino, died in Kenya in March following a series of infections, leaving only two females of his subspecies alive.

Artificial insemination could be the means of saving a threatened rhino species, researchers at a California zoo say TONY KARUMBA, AFP/File

Rhinos have few predators in the wild due to their size.

However, demand for rhino horn in traditional Chinese medicine and dagger handles in Yemen fueled a poaching crisis in the 1970s and 1980s that largely wiped out the northern white rhino population in Uganda, Central African Republic, Sudan and Chad.

A final remaining wild population of about 20-30 rhinos in the Democratic Republic of Congo died out during fighting in the late 1990s and early 2000s, and by 2008 the northern white rhino was considered extinct in the wild.