Scientists started working back in the 1990s to genetically engineer a soybean that’s oil would be free of artery-clogging trans fats, a product farmers think will appeal to consumers as well as food-makers and fast-food chains.

But even though federal regulators approved a soybean variety in 2010 developed by a unit of DuPont, the crop is still only being grown on limited acreage under strict rules to ensure it is kept separate from other soybeans.

The reason is at the heart of a major issue facing U.S. and European negotiators as they try to work out a trade deal, known as the Transatlantic Trade and Investment Partnership, that can get ratified by Congress.

DuPont has been unable to get the European Union’s approval for the new product, one of an array of genetically engineered crops that are stalled in an EU approval process, even though the company first applied for EU approval in 2007.

DuPont doesn’t plan to market the biotech seeds in Europe and doesn’t expect the cooking oil to sell there either, because of European resistance to many genetically engineered foods, which are produced from genetically modified organisms.

DuPont’s concern, and the concern of U.S. farmers, is that a soy shipment to Europe could be accidentally contaminated with traces of the new soybean, which goes by the trade name Plenish. So, until the EU approves the crop, sales and cultivation of the seeds will continue to be restricted in the United States.

Most of the soybeans now grown in the United States are genetically engineered. The EU allows importation from the United States of some GMO varieties it has approved already — so the concern is about contamination by unapproved beans such as Plenish.

Even a small amount of contamination could lead to a shutdown of soybean trade. Foreign countries don’t hesitate to block shipments of U.S. farm commodities if it’s possible they contain minute amounts of biotech products those nations haven’t approved. Japan and South Korea both imposed bans on U.S. wheat this spring, when stray plants of an unapproved biotech variety were discovered growing in Oregon.

“The problem is that Europe just delays and delays and delays” making decisions on applications, said Matt O’Mara, director of international affairs for food and agriculture at the Biotechnology Industry Organization, the trade group that represents biotech seed giants such as DuPont and Monsanto Co., which has developed a similar soybean to DuPont’s. “We want there to be a commitment to change this practice, and we believe TTIP is the most effective way to do it.”

However, in a statement, EU officials expressed confidence that a TTIP deal would not require any changes in European laws or hinder the EU’s approval process. “The safety assessment which EFSA carries out before any GMO is placed on the market and the risk management procedure will not be affected by the negotiations,” the statement said.

Opponents of biotech crops say they’re worried the administration will use the negotiations to eliminate European barriers to biotech products and to make it more difficult to ever erect similar restrictions in the United States. Many groups opposed to the technology have been pushing for state and federal labeling rules similar to those in Europe.

In a letter to U.S. and EU trade officials last month, an array of American and European advocacy groups expressed particular concern about preserving the EU’s right to use what is called the “precautionary principle” in evaluating new food products, including GMOs. The precautionary principle puts a heavier burden on regulators to be sure a product poses little or no risk of harm. U.S. agribusiness groups have urged the administration to address that issue in the negotiations.

“Those of us in the European Union reject any weakening of the use of the precautionary principle, while those of us in the United States demand that our negotiators not make any proposal that would preclude its use in the future,” the groups said in the June 24 letter. The organizations that signed the letter included the Center for Food Safety, which has fought U.S. approvals of biotech crops, and the Institute for Agriculture and Trade Policy.

While the biotech industry remains concerned about the precautionary principle, “we’re trying to find a practical way forward” to accelerate approvals, O’Mara said. Biotech companies have 74 applications awaiting approval in the EU, 22 of which have been approved by the European Food Safety Authority. Some of those 22 are renewals, rather than new applications. Even if the food safety organization decides a product is safe, the European Commission still has to render its OK. Some of the applications have been awaiting final action for as much as three and a half years.

O’Mara says the U.S. industry isn’t challenging the EU’s biotech regulations themselves or its labeling requirements for GMOs. “I don’t think we’re anticipating competitive nirvana as a result of the TTIP,” he said.

The biotech industry has largely given up on being able to sell GMO seeds in Europe, though Europe does still import some GMO soybeans, oil and meal. Earlier this month, Monsanto Co. became the latest firm to announce that it would no longer seek approvals for cultivating crops there. However, more and more farmers are growing the crops in other parts of the world, so the EU resistance to imports will continue to be a concern to the industry.

A record 17.3 million farmers worldwide grew 420 million acres of biotech crops in 2012, up 6 percent from 2011, according to an annual survey by the International Service for the Acquisition of Agri-biotech Applications. Developing countries, including Brazil, Argentina, China and India, for the first time grew more of the crops than the United States and other industrial countries, 52 percent versus 48 percent. Plantings in Brazil jumped 21 percent, to more than 90 million acres, second only to the United States at 172 million.

U.S. farmers are eager to see new soybean varieties succeed, because soybean oil has been fast losing market share to other products such as imported palm oil since the Food and Drug Administration decided a decade ago to require food manufacturers to start listing trans fat content on product labels. Partially hydrogenated soybean oil, the source of the trans fats, had long been favored by fast-food restaurants and companies that make cookies, pastries and baked goods. In fryers, the oil would last longer without going rancid than alternative products.

Oil from the gene-altered soybean Plenish, as well as from the Monsanto version, which are relatively high in oleic fatty acid, the main fatty acid found in olive oil, mimic key cooking characteristics of partially hydrogenated oil without the trans fats, said Russ Sanders, director of food and industry markets for DuPont Pioneer.

Imported palm oil has replaced soybean oil in many products, including cookies, and “has really filled the gap when we went into the trans fat issue,” said South Dakota farmer Lewis Bainbridge, a director of the United Soybean Board, the industry’s promotional arm. “We’re hopeful that with a home-grown product, which is what we’re trying to achieve here, that we can be competitive here.”

The industry’s goal is to grow 18 million acres of the new high-oleic varieties by 2023, or about 20 to 25 percent of total soybean acreage, he said. For now, the main impediment to expansion isn’t the EU approval delay so much as the amount of time it takes to breed the trait into the highest-yielding varieties for each region of the country, he said.

Just 100,000 acres of DuPont’s high-oleic soybeans are being grown this year, Sanders said. Until the EU gives its OK to the new soybean, DuPont’s crop is being grown only under contract between farmers and four major processors, including Cargill Inc. and Bunge Ltd. The contracts ensure the crop is stored and trucked under strict requirements so it doesn’t get mixed with other soybeans.

“We’re moving forward cautiously because we want to make sure we protect the integrity of the supply chain,” Sanders said.