Boris Johnson today vowed to drive a 'hard bargain' with the US as the government sets out its trade demands.
The UK is pushing for a Transatlantic deal at the same time as negotiating a new relationship with the EU - in the hopes that will increase pressure on Brussels to offer good terms.
Ministers are due to publish the mandate for talks with Washington later.
But Mr Johnson is also facing pressure from unions not to 'cosy up' to Donald Trump in his haste to cut a deal.
The government says it wants to open up opportunities for British businesses and investors in the US through a free trade pact, but insists the NHS will not be up for grabs.
The British team also wants to guarantee high standards and protections for British consumers and workers, including on animal welfare.
Boris Johnson (pictured left yesterday) has been warned not to 'cosy up' to Donald Trump (right at the White House yesterday) in looming trade talks
Ahead of the mandate being formally revealed, Trade Secretary Liz Truss said: 'In a trade deal with the US, we will not diminish our food safety standards and we will also not put the NHS on the table.
'If we don't get the deal we want we will be prepared to walk away.'
Mr Johnson said: 'We have the best negotiators in the business and of course, we're going to drive a hard bargain to boost British industry.
'Trading Scottish smoked salmon for Stetson hats, we will deliver lower prices and more choice for our shoppers.
'Most importantly, this transatlantic trade deal will reflect the unique closeness of our two great nations.'
The talks will take place in parallel alongside the bartering with the European Union over a post-Brexit relationship.
Ministers have repeatedly faced demands to rule out chlorinated chicken and hormone-treated beef being imported from the US in any deal, with animal welfare and environmental concerns raised.
Labour accused ministers of making 'false promises' over commitments to protect the NHS and standards.
Shadow international trade secretary Barry Gardiner said: 'This is a Government that has sought, at every opportunity, to resist efforts to lock in our high standards and to ensure robust protections for our NHS.
'Their false promises are meaningless - they have said they won't undercut our food standards while briefing that chlorinated chicken and hormone-fed beef are perfectly acceptable.
'That is why there