Farmers and growers will protest in London calling for the free trade negotiations between the EU and the US to be scrapped.
The Transatlantic Trade and Investment Partnership is the biggest bilateral trade deal in history. The aim is to harmonise standards and regulations.
The agreement could boost the UK economy by £10 billion and could give opportunities for food producers in the UK and their products, such as high value dairy, lamb and beef.
Roger Williams, MP for Brecon and Radnorshire, said: “While I welcome the great opportunities that this will give the quality Welsh products, we must be aware that American food producers benefit from lower regulatory costs on such things as animal welfare, hygiene, and the use of genetically modified and synthetic hormones.
"These give American farmers an advantage and so we must ensure during the negotiations that we have a level playing field. These issues must be resolved before we can wholeheartedly enter into this trade agreement.”
But the Landworkers' Alliance said: "If the corporations involved get their way we will see the increasing import of inferior produce into the EU which will depress prices for farmers."
"Important health and safety standards are at risk with US negotiators pushing to remove regulations on Genetically Modified foods, increase the quantity of pesticide residues permitted and allow the use of dangerous chemicals, antibiotics and growth hormones previously banned in the EU."
Humphery Lloyd a grower and member of the Landworkers’ Alliance said: "The EU's pre-negotiation concession to allow imports of American beef decontaminated with lactic acid spray is indicative of what is to come - quality in farming and food processing will be driven down into a race to the bottom with farmers and the public loosing out."
"This agreement is shaping up to be a hand out to corporations at the expense of public health and food security. If we degrade our import standards in line with the demands consumers will have more than just chlorine soaked chicken to worry about - this will force farmers out of business and seriously erode UK food sovereignty. We demand that the government stops selling out UK farmers and consumers in these negotiations."