WASHINGTON (Reuters) - Research involving genetic modification of human embryos, though controversial, is essential to gain basic understanding of the biology of early embryos and should be permitted, an international group of experts said on Wednesday.

The statement was issued by members of the so-called Hinxton Group, a global network of stem cell researchers, bioethicists and policy experts who met in Britain last week.

The group said it did not currently favor allowing genetically modified human babies to be born.

"However, we acknowledge that when all safety, efficacy and governance needs are met, there may be morally acceptable uses of this technology in human reproduction, though further substantial discussion and debate will be required," the group said in a statement.

The expert group cited the "tremendous value to basic research" and said the science of gene-editing "will continue to progress rapidly, and there is and will be pressure to make decisions scientifically and for funding, publishing and governance purposes."

The U.S. National Institutes of Health (NIH), which funds biomedical research, refuses to provide money for any use of such gene-editing technologies in human embryos.

"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," NIH Director Dr. Francis Collins said in April.

Collins at the time noted that researchers in China had described experiments in a non-viable human embryo to modify the gene responsible for a potentially fatal blood disorder using a gene-editing technology.

Debra Mathews of the Johns Hopkins Berman Institute of Bioethics in Maryland and a member of the Hinxton Group steering committee said despite deep moral disagreement on the subject "what is needed is not to stop all discussion, debate and research." Mathews called for weighing the potential benefits and harms of human genome editing for research and human health.

Robin Lovell-Badge, a member of the Hinxton Group steering committee and head of the Laboratory of Stem Cell Biology and Developmental Genetics at the Francis Crick Institute in Britain, said, "Genome-editing techniques could be used to ask how cell types are specified in the early embryo and the nature and importance of the genes involved."

"Understanding gained could lead to improvements in IVF (in vitro fertilization) and reduced implantation failure, using treatments that do not involve genome editing," Lovell-Badge added.

(Reporting by Will Dunham; Editing by Himani Sarkar)