The FDA last week said meat and milk from cloned cattle, swine and goats and their offspring were as safe to eat as products obtained from traditional animals. Before then, farmers and ranchers had followed a voluntary moratorium that prevented the sale of clones and their offspring.

'There is no feeling that this will ever become a way of mass producing animals,' Mr Stephen Sundlof, director of FDA's Center for Food Safety and Applied nutrition, told reporters on Thursday.

He noted that another reproductive technique used in agriculture, in vitro fertilisation and embryo transfer, has been used to create only a small portion of the millions of animals on US farms.

It could take four or five years before consumers are able to buy clone-derived food on a wide scale as animals need to be cloned, mature and give birth. So far, several major food companies including Tyson Foods, the largest US meat company, and Smithfield Foods have said they would avoid using cloned animals.

The FDA and the small cloning industry both maintain cloned animals are as safe as regular animals.

'At this point in time we don't believe there are offspring out there in the nation's food supply system,' said Mr Sundlof.

'We are not really concerned with tracking progeny because they are in every respect a normal animal.'

Even as the FDA unveiled its final rule, the Agriculture Department has asked the cloning industry to prolong the ban on selling products from cloned animals during a 'transition' period expected to last at least several months.

Democratic lawmakers Senator Barbara Mikulski of Maryland and Representative Rosa DeLauro of Connecticut have introduced legislation that would require a label on products from cloned animals or their offspring. Some state lawmakers also have introduced similar legislation.

'If cloned food is safe, let it onto the market, but give consumers the information they need to avoid these products if they choose to,' said Ms Mikulski.

Proponents have touted cloned animals as safe and hope the technology will create animals that produce more milk, better meat and are more disease-resistant.

Critics still contend not enough is known about the technology to ensure it is safe and they also say the FDA needs to address concerns over animal cruelty and ethical issues. -- REUTERS