She said she did not think US Treasury Secretary Steven Mnuchin's proposal to drop tariffs, non-tariff trade barriers and subsidies was serious, pointing out the US had laws and subsidies protecting American industries.
"These possible negotiations will not concern agricultural goods, there may be some reference to soybeans", an European Union official said on condition of anonymity, adding that the increased imports were already reflected on the market.
But Juncker, who last week signed a new economic agreement with Japan, is not expected to make a specific trade offer as he meets Donald Trump.
The Trump administration is crafting a $12 billion emergency aid package to help farmers affected by tariffs on their crops, the U.S. Department of Agriculture said Tuesday.
Eric Schweitzer, president of the German Chambers of Industry and Commerce (DIHK), said it was up to the United States now to rebuild a basis of trust with Europe, and remove the tariffs.
She said the United States goods would include machinery, agricultural and high-tech products, among others.
The pair also agreed to hold off imposing any further tariffs while negotiations take place, and to work towards reform of the World Trade Organisation.
Juncker, joined by EU trade chief Cecilia Malmstrom, was expected to raise the possibility of talks between major auto-exporting countries aimed at reducing tariffs on the auto trade worldwide, according to a senior European official who spoke on condition of anonymity to describe internal deliberations.
The overtures are a last-ditch attempt to persuade him from imposing tariffs on European vehicle exports to the US, in what could deal a serious blow to the bloc's economy. Trump is on Thursday visiting Granite City Works, an IL plant owned by US Steel that announced last month tariffs allowed it to increase production.
Canada, Mexico and China - the main target of Mr Trump's trade offensive - also have hit back with steep duties on USA goods, and have filed complaints against Washington at the World Trade Organisation.
President Donald Trump declared victory for American farmers Thursday after brokering a ceasefire in a trade dispute with the European Union, but it is unclear how soon it will bring relief to those hurt by tit-for-tat tariffs.
Specifically, the Journal's sources say that European Union representatives made use of "colorful cue cards" that they thought would help keep the president's attention during meetings.
Farmers have been a casualty of Trump's trade war.
"Either a country which has treated the United States unfairly on Trade negotiates a fair deal, or it gets hit with Tariffs".