London(CNN Business) The United States is giving the United Kingdom a preview of what it can expect from take-no-prisoners trade negotiations after Brexit.

The Trump administration on Thursday outlined its goals for a free trade deal with Britain in a document that takes a tough line on agricultural products and warns the United Kingdom against getting cozy with China.

The list of priorities, which runs to 18 pages, makes sobering reading for a British government that was hoping for a quick deal on trade with the word's largest economy after Brexit.

"This is an uncompromising document from the US point of view, with no mention of mutual benefit," said David Henig, the director of the UK Trade Policy Project and a former UK trade official.

Supporters of Brexit have touted the ability to strike new trade deals with America and China as a major benefit of leaving the European Union, which conducts trade policy on behalf of its members. And President Donald Trump had promised the United Kingdom a "very, very big deal, very very quickly."

But the document makes clear that the United States will be seeking major concessions in exchange for an agreement. Without the backing of the European Union, Britain will be under pressure to accept if it wants a deal.

What the Americans want

The US administration wants to secure "comprehensive access" for agricultural goods in Britain by reducing or eliminating tariffs. It also wants other barriers to US exports removed.

Scrapping those barriers could open Britain's door to genetically modified crops, animal feed with antibiotics and chlorine-washed chicken products that are banned in the European Union but common in the United States.

Henig said that the United States sees Brexit as an "opportunity to ensure the United Kingdom follows the US approach in areas such as food standards."

That would be politically unpopular in Britain. But it would also be problematic for another reason.

The United Kingdom is hoping to maintain a close trading relationship with the European Union, its biggest trade partner, after Brexit. To do that, it needs to remain aligned with strict EU safety and environmental rules.

Trump has previously warned that the Brexit deal Prime Minister Theresa May negotiated with the European Union, which includes a transitional period of nearly two years, could hinder trade with the United States.

The UK government said in a statement that the document shows the United States' "commitment to beginning talks as soon as possible." It said a deal with Washington that "maintains our high standards ... is a priority."

China threat

The US document also warns Britain that it will take "appropriate action" if the country negotiates a trade deal with a "non-market country" — which experts said is a reference to China.

"It's attempting to allow the United States to withdraw the deal if it doesn't like any agreement the United Kingdom makes with China," said Peter Holmes, a trade expert who teaches economics at the University of Sussex.

The provision also serves as a warning to China.

"[It would also be] a signal to China, if signed, that future cooperation will be determined by a larger power," said Henig.

Experts say the tough line taken by the United States reflects the reduced bargaining power the United Kingdom will have once it leaves the European Union.

It will negotiate as a country of 66 million, while the European Union represents a bloc with 500 million citizens. Other countries also know that the United Kingdom will be highly motivated to replace free trade deals it lost because of Brexit.

South Korea and Japan have already indicated they will demand concessions on trade in return for new deals with the United Kingdom to replace those it has as an EU member state.