National Institute of Health director Francis Collins spoke out against research that editing human genes. The decision comes after China used gene-splicing technology to remove genes from an embryo.

Chinese scientists altered the DNA of a non-viable embryo to try to cure a blood disorder. While the gene editing didn’t work, it has the potential to permanently change genetics.

“NIH will not fund any use of gene-editing technologies in human embryos,” said Collins in a statement in a statement on the NIH website.

“The concept of altering the human germline in embryos for clinical purposes has been debated over many years from many different perspectives, and has been viewed almost universally as a line that should not be crossed,” added Collins.

Collins noted that NIH will support other innovations in genetics. “NIH will continue to support a wide range of innovations in biomedical research, but will do so in a fashion that reflects well-established scientific and ethical principles,” said Collins.

Some geneticists say that editing DNA could lead to parents choosing to edit any genes that carry genetic disorders children may have, like Down Syndrome.

“Creating genetically modified human beings could easily lead to new forms of inequality, discrimination and societal conflict,” said Marcy Darnovsky, executive director of the Center for Genetics and Society.

While many scientists are against gene editing, some are in favor of the controversial method.

“I am not in favor of the NIH policy and I believe that the Chinese paper shows a responsible way to move forward,” says David Baltimore, a biologist at the California Institute of Technology in Pasadena.