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Yves Logghe, Associated Press
European Commissioner for Agriculture Dacian Ciolos, right, and U.S. Secretary of Agriculture Tom Vilsack, address the media at the European Commission headquarters in Brussels, Tuesday, June 17, 2014.

BRUSSELS — Agriculture Secretary Tom Vilsack has come to Europe to make the U.S. case on disputed issues in farm trade, as the Obama administration and European Union negotiate a new trade and investment agreement

Agriculture is a perennial hot-button topic in trans-Atlantic relations, and Vilsack said Tuesday it's hard to imagine any deal being approved by the U.S. or EU if it doesn't include an agricultural component.

Grounds for disagreement are numerous.

The U.S. wants European authorities to allow genetically modified crops and food processing techniques including the use of chlorinated rinses to process poultry carcasses. Meeting with reporters, Vilsack said that if "sound science" shows such practices to be safe, European consumers should have the option of purchasing the food that results.

EU officials and European consumer groups are much less enthusiastic about such techniques, or flatly reject them. Ministers from the trade bloc's 28 member countries agreed in principle last week to empower any EU country to prohibit or restrict the growing of genetically modified crops on its territory.

Some European countries are also claiming the sole right to market certain food products under names they consider their exclusive cultural heritage, such as feta cheese from Greece.

After talks with Vilsack on Tuesday, EU Agriculture Commissioner Dacian Ciolos said he was convinced that Europeans and Americans need "a better understanding of our realities" if negotiations for the proposed Transatlantic Trade and Investment Partnership are to succeed.

Vilsack said European consumers should be given options, including food grown or processed in novel ways deemed safe in the U.S.

"If we are truly interested in feeding the world, truly interested in doing so with less pesticides and chemicals and truly interested in doing so with more inclement weather and more intense weather patterns because of climate change, we are going to have to adopt science," he said.

On Monday, Vilsack met in Luxembourg with agriculture ministers from the EU member states. U.S. officials said he would also be visiting France and Ireland.