Europe's reluctance to buy beef grown with hormonal growth promotants or genetically modified foods from the US has exposed an enormous gulf that threatens the world's biggest trade pact, industry and labour groups told EU and US negotiators this week.

Reuters reported that eight months into talks to create a transatlantic free trade agreement encompassing almost half the world's economy, divisions remain over opening up to each other’s goods, rules governing the names of foods, processing standards, the use of growth enhancing tools and genetically modified food.

"There is an enormous gulf between the EU and US positions," said Michael Dolan, a lobbyist for the US Teamsters union, who rejected the idea that the European Union should be the only market to call Greek-style cheese 'feta'.

He told negotiators in a forum session that a trade deal was likely to be “smaller and more modest than its ambitions, because of so many intractable issues."

Tensions over food, which have bedevilled many trade talks around the world, risk eroding already fragile public support for a deal that advocates say would increase economic growth by around $100 billion a year on both sides of the Atlantic, Reuters said.

Negotiators aim to finalise a deal by the end of this year.

Mindful of the huge protests surrounding global trade talks in the 1990s, EU and US negotiators holding a fourth round of talks this week in Brussels took the unusual step of not only receiving lobbyists, but also letting in the media.

What little public awareness there is about the Transatlantic Trade and Investment Partnership (TTIP) could be distorted by anti-globalisation protesters, EU ministers have warned.

At risk is a pact creating a market of 800 million relatively affluent people where business could be done freely, building on the almost $3 billion of transatlantic trade in goods and services each day.

Difficulties over agriculture bode poorly for the talks because EU and US negotiators are seeking a far more a sophisticated agreement, going beyond farm goods to bring down barriers across all industries and businesses.

Even animal welfare is sensitive in a proposed accord where both sides would recognise each other’s standards to oil the wheels of commerce. Europeans said they consider US standards concerning the slaughter of animals as being far lower than in the EU.

Even without such issues, US farmers complain that the farm trading relationship is unfairly skewed in Europe's favour and want it addressed in the trade talks, Reuters said.

The EU exported $16 billion worth of farm goods to the US in 2012, much more than the $10 billion in farm good trade in the other direction, partly because of EU rules banning imports of genetically modified food for human consumption.

“Our trade could be way bigger," said Douglas Nelson, an adviser for farm group CropLife America. Floyd Gaibler of the US Grains Council said: "The TTIP is a way to normalise trade with the European Union."

But barely a week goes by that EU trade commissioner Karel De Gucht, who handles commerce issues for the EU's 28 member states, says that European regulation of genetically modified food will not change, even if a deal is done with Washington.

The EU is also closed to US beef from cattle administered with HGPs. Some Europeans are worried about what impact GM crops and hormone-enhanced beef – often dubbed "Frankenstein Food" – might have on health and the environment, Reuters said.

"The US and the EU have the highest standards of food safety. How is it that we have such different ideas about how to achieve those standards?" said John Brook, regional director of the US Meat Exports Federation.

"Have you ever heard about a European on holiday in the US being fearful of eating US meat? Everyone raves about the experience of eating in a US steak house," he said.