The achievement, which according to the Washington Post was carried out last August, differs from the celebrated cloning of Dolly the sheep in that the monkeys were created from embryos, rather than an adult animal. This means that the cloned monkeys are not genetically identical to an existing animal - one of the most controversial aspects of the experiment carried out by Professor Ian Wilmut and his colleagues in Scotland.
However, the technique was in other respects broadly similar. First, scientists at the Primate Research Center in Beaverton, Oregon, created monkey embyros by standard in vitro fertilisation. Once the embryos had divided into eight cells, they took a set of chromosomes from each embryo and inserted them into a fresh egg cell whose DNA had been removed.
Of these, nine developed into standard embryos and were implanted into female monkeys, three of whom became pregnant. One foetus died, but the other two survived and are said to be perfectly normal.
The pair, created by using the eggs and sperm of the same parents, are siblings, but they are not genetically identical. However, according to scientists there is no reason why identical monkeys could not be created from different cells of the same embryo, nor why clones of living monkeys could not be achieved, as in the case of Dolly the sheep. At the very least, it is another pointer that human cloning, in scientific terms, is feasible.
The most practical consequences, however, could be for drug research and development, carried out on "made-to-measure" colonies of animals, created with specific and identical characteristics. This could lead to new techniques to help infertile women, said Dr Don Wolf, head of the Oregon research team.
Professor Wilmut, who led the team at the Roslin Institute in Edinburgh and PPL Therapeutics to produce Dolly, said the Oregon achievement was two steps away from cloning adult monkeys .
"At the eight-cell stage all the cells are much the same. It's a necessary step but it's well back." The next step would be to clone later-stage embryos - as the Roslin and PPL team did in 1995, when they took nine- day-old embryos and put the DNA from individual cells into emptied egg cells. That produced two sheep, Morag and Megan, which are now 18 months old.
"Of course, there's nothing to stop the American scientists from trying to produce monkey versions of Morag and Megan tomorrow," said Professor Wilmut.Reuse content