The global debate on genetically engineered food is reaching a fever pitch this week as agricultural ministers, scientists, executives and politicians from around the world meet at pro-biotechnology conferences on both the East and West coasts of the United States. The United States is the biggest producer and consumer of genetically improved crops, but many countries avoid them on the grounds that they may be harmful to humans and animals. The European Union has imposed a ban on genetically modified foods. As a result of the ban, the world?s largest developer of genetically altered crops, the U.S.-based Monsanto Company, has been losing profitable deals.

For centuries, humans have tried to improve plants by selective breeding and controlled pollination. Through these conventional methods hundreds of thousands of genes are transferred randomly from one plant to another to combine their traits.

Today, scientists can be much more precise. They can select only one or two genes with desired traits and transfer them to a plant to enhance its growth, its resistance to drought or disease or its tolerance to chemicals. This new technology has been used in agriculture to increase production of crop plants such as corn, wheat, soybean or cotton. The Monsanto Company also produces pesticides and herbicides that kill insects or weeds, but do not harm the genetically modified plants.

At Monsanto?s Life Sciences Research Center in St. Louis, Missouri, nearly 1,000 researchers work in some 300 laboratories on the site. Robotic arms, like the ones on a space shuttle, travel up and down a three-meter track. They pick up trays that look like CD?s stacked in a CD rack and place them in slots on the laboratory bench.

Bill Kosinski, a biotechnology educator at Monsanto, says these stacked trays are sets of test tubes for discovering new drugs, pesticides and herbicides. ?You first identify a key enzyme responsible for a particular disease,? he says. ?You extract that enzyme and then you challenge it with as many chemical compounds, as many potential drugs as you can get your hands on.?

Mr. Kosinski says each test tube contains a different chemical molecule and each undergoes a set of biological procedures. The data for each sample is fed into the computer and it tells scientists whether or not a particular molecule has the potential to be used to fight a crop or livestock disease.

Some 20 years ago, it would take one scientist a whole day to process five samples. Today, the three robotic arms at Monsanto can process 40,000 to 50,000 samples a day.

Once a pharmaceutical company, Monsanto focuses mainly on agriculture today, with the goal of increasing global food production. Mr. Kosinski says the St. Louis research center is capable of producing custom-made plants to grow in less than favorable climates or fight a particular pest.

?We will take your insect," he says, "the one that?s eating your crop plant, and feed it as many different protein materials as we can get our hands on and we will work with academics. In St. Louis, we work with the Missouri Botanical Gardens."

"These folks go out and collect novel biological specimens," he says. "We?ll take those materials back to this site, extract all the possible proteins - all living things are composed of proteins - then we?ll put one unique protein in each of one of these wells on this research muffin-pan type system. We?ll then overlay them with egg or larva of your insect pest, the one that?s giving you the problem. We?ll cover the plate, we?ll incubate for seven days, then we?ll come back and evaluate the plates.?

Once the scientists identify the protein that kills or slows down the growth of larvae, they extract its pest-killing genes, which will be inserted into a crop plant, such as corn (maize), soybean, or cotton to make it resistant to the pest.

Monsanto has developed a number of disease-free plants that grow better in poorer soil, produce more crops and even taste better. Many scientists believe such crops could reduce the global problem of famine. But many people oppose the company?s genetic manipulation of food plants for fear they may be unhealthy for humans or animals.

Mark Buckingham, a British scientist at Monsanto, says the company?s products have been thoroughly tested to make sure they deliver benefits without risks. He says traditional broad-spectrum herbicides and pesticides are much more harmful than Monsanto?s best-selling Roundup brand.

?In order to control one insect,? he says, ?under a traditional system a farmer might spray the whole field, maybe more than once, maybe several times. That would kill all the insects in the field, whether they were just passing through, whether they were pest species, whether they were beneficial insects. One of the beauties of biotechnology is that you can specifically target the pest insect and the products. The crops that we have developed are very carefully tested to make sure that it is just that insect that is targeted.?

Mr. Buckingham says Monsanto makes sure that plants contain nothing harmful to people by carefully choosing the genes. Those for insect-protected crops largely come from natural bacteria that have been used in agriculture for many years.

?We have taken that technology one step further,? he says, ?by taking a gene from that natural bacterium and putting it into the crop. We?ve given the crop the ability to protect itself. So that understanding where that gene comes from is an important reassurance that it is from something that has been used in crop production and food production for many years with the history of safe use.?

But these assurances have not pacified critics who point to the company?s earlier products that have been found harmful or potentially harmful. One is Agent Orange, which was used in the Vietnam War to defoliate the jungle and later determined to be harmful to humans. Monsanto?s artificial sweetener NutraSweet has been under attack as potentially harmful.

Although there is no scientific evidence that genetically engineered plants cause any harm, the European Union has banned the import of genetically altered food, saying the technology is too new to be sufficiently tested.

As a result, countries depending on their food exports to Europe refuse to grow Monsanto crops. Even some of those that suffer from severe famine have rejected them. The United States has filed a complaint with the World Trade Organization against the European Union for its moratorium on biotech products. It is now pushing its biotechnology on the international stage.

Speaking to biotechnology scientists from developed countries at the Biotechnology Conference this week in Washington, President Bush said genetically modified crops are needed to reduce famine in Africa. ?In our own country we see the benefits of biotech with food prices and good land conservation practices,? he says. ?Yet the great advantages of biotechnology have yet to reach developing nations in Africa and other lands where these innovations are now most needed.?

But even as Mr. Bush spoke on the East Coast, anti-biotech activists protested at the Ministerial Conference on Agricultural Science and Technology on the other side of the country in Sacramento, California.