Scientists have cloned a cat, opening the door to what some experts say will be the first large-scale commercial use of cloning to reproduce beloved pets.

The effort was supported by a company, Genetic Savings and Clone, of College Station, Texas, and Sausalito, California, which wants to offer cloning to dog and cat owners. It is investing $3.7 million in the project. 

The study will be published in the February 21 issue of Nature but the journal released the paper on Thursday because the result, although not the details of the study, had become public. "The commercial future of cloning is absolutely in animals," said Arthur Caplan, an ethidst at the University of Pennsylvania. "To put it bluntly, human cloning will turn out to be of interest only to the vain or the desperate and companies know this." However Dr Caplan said he had two concerns. "Are you preying on the grief and desperation that pet owners often have when they lose a pet to promise them something more than cloning can deliver?" he asked. 

"If cloning creates animals that suffer and die young, can it be justified?" he said. While some cloned animals have grown up to be perfectly normal, others have died in infancy of severe medical problems. 

The cloned cat, called cc, for carbon copy, is a genetically identical copy of a two-year-old female cat. Rainbow, that was not anyone's pet. But Rainbow and cc do not look alike, illustrating that identical twin cats may not have identical coats. The cat cloning project failed at first but succeeded on the-second try and cc was born on December 22, healthy and normal. But the company's dog cloning project, which began several years ago and is directed by the same researchers, still has not succeeded. 

Duane Kraemer, a member of the cat cloning team and professor of veterinary medicine at Texas A&M University, said one reason for tins was that scientists had much. more experience working with cat eggs and embryos. 

Unlike cats, which ovulate when they are mated, making it easy to time the production of eggs, dogs are unpredictable. Unlike other mammals that excrete mature eggs, dogs excrete immature eggs from their ovaries, making it hard to obtain the mature eggs needed to start the cloning process.

Lou Hawthorne, the chief executive of Genetic Savings and Clone, said cat cloning was almost an, afterthought for the company. "We had thought this was something that mostly dog owners would be interested in," he said. But after the company heard from thousands of pet owners and did market research, it realised that the cat cloning market could be huge, he said. For now, he said, the company was storing tissue from cats and dogs for a fee, so that owners could try to have their pets cloned in the future. "Pet owners will have to be patient and realise that they would be expected to bear some of the research costs," he said, adding that he could not estimate what cat cloning would cost.