New York: Scientists have developed a technique for extracting human embryonic cells without destroying embryos, according to a report in the magazine Nature.

The method appears to get round a basic ethical objection to stem cell research and is the same procedure used in IVF when one cells is removed to analyse for genetic diseases.

Dr Robert Lanza, vice president of US biotech group Advanced Cell Technology and leader of the tema involved said there is no rational reason left to oppose this research.

Researchers from Advanced Cell Technology have generated stem cell cultures by plucking individual cells from newly fertilized embryos, which are not harmed.

The new technique would be performed on an embryo when it is two days old, after the fertilized egg has divided into eight cells, known as blastomeres.

In fertility clinics, one of these blastomeres can be removed for diagnostic tests, such as for Down’s syndrome, and the embryo, now with seven cells, can be implanted in the mother if no defect is found.

Up to now, stem cells have been derived from slightly older embryos. Harvesting these cells destroys the embryo.

Last year, Lanza reported that embryonic stem cell cultures could be derived from the blastomeres of mice. He now says the same can be done with human blastomeres.

Hardline critics of embryo research, however, are unlikely to accept the manipulation even of a single embryonic cell, which they say could theoretically become a human being.

US President George W. Bush last month vetoed a bill that would have required the federal government to fund experiments with newly created human embryonic stem cells.