For the first time ever, American scientists have successfully edited the DNA of a human embryo — in the attempt to correct genes that cause inherited diseases, a report says.

Researchers from Oregon Health and Science University in Portland managed to modify numerous one-cell embryos using a controversial technique called CRISPR, according to MIT Technology Review.

Sources told the school magazine that the team, led by US-based biologist Shoukhrat Mitalipov, was able to safely inject gene-editing chemicals into human eggs near the moment of fertilization.

While the embryos were not allowed to be developed for more than a few days, the researchers ultimately proved that they could be efficiently edited in the attempt to correct genetic disorders.

Up until now, China was the only known country to carry out the practice. But they only managed to make their desired DNA changes on a small number of cells, creating an effect known as “mosaicism.”

Experts describe this as a condition in which cells within the same person have a different genetic code or makeup.

Mitalipov’s team, however, was able to prevent this from happening.

“They significantly reduced mosaicism,” explained one researcher, who chose to remain anonymous.

The milestone means scientists in the US are officially one step closer to engineering the first genetically modified human beings on earth.

“It is proof of principle that it can work,” the researcher said. “I don’t think it’s the start of clinical trials yet, but it does take it further than anyone has before.”