By Ben Hirschler

LONDON (Reuters) - Scientists from the United States, China and Britain will come together to discuss the future of human gene editing, which holds great promise for treating diseases but also has the potential to create "designer babies."

The Chinese Academy of Sciences and Britain's Royal Society said on Monday they would join the U.S. National Academy of Sciences in co-hosting an international summit on the topic in Washington on Dec. 1-3.

The technology, called CRISPR-Cas9, allows scientists to edit genes by using genetic "scissors" that operate a bit like a biological word-processing program that can find and replace defects.

CRISPR has excited academic researchers and drug companies alike, since it may allow them to rewrite the DNA of diseased cells. But it has also raised serious ethical concerns due to the potential to alter the genetic code of embryos.

"Human gene editing offers great promise for improving human health and well-being but it also raises significant ethical and societal issues," said Paul Nurse, president of the Royal Society.

"It is vital that we have a well-informed international debate about the potential benefits and risks, and this summit can hopefully set the tone for that discussion."

In addition to the Washington summit, an expert committee will issue a report next year with recommendations to guide the responsible use of human gene editing.

China plays an important role in the debate since a group at Sun Yat-sen University in Guangzhou published results in April of an experiment to alter the DNA of human embryos using CRISPR.

Altering the DNA in this way could produce unknown effects on future generations, since the changes would be passed on to offspring. Such germline engineering, affecting eggs, sperm or embryos, is very different from altering non-reproductive cells in order to fight a disease.

The Guangzhou case provoked widespread concern, but Chinese Academy of Sciences President Chunli Bai said on Monday his country wanted "to work together with international communities for the proper regulation and application of such technology."

China is a growing force in life sciences, particularly in gene editing, with a burgeoning patent portfolio, according to a Reuters analysis in June.

Pharmaceutical companies including Novartis and AstraZeneca are meanwhile investing in the new technology and a number of standalone biotech firms have been set up, including Intellia Therapeutics, which raised $70 million in a fundraising this month.