If confirmed in a forthcoming peer-reviewed journal, the new research would constitute the first attempt at American gene-editing, a field which has so far been held back by fears of “designer babies”.

Shoukhrat Mitalipov, who led the study, declined to confirm the results ahead of their formal publication, however scientists on his team told MIT Technology Review they showed it was possible to safely and efficiently correct defective genes causing inherited disease.

The embryos were allowed to develop only for a few days before being destroyed and there was never an intention to implant them into a womb.

The reported experiment may nevertheless mark a milestone on a journey towards genetically modified humans.

In the last two years, scientific opinion in the US has grown more sympathetic to germline editing, where a genetically modified child can pass on changes to future generations.