The spotlight is trained once again on the possibility of a UK-USA trade deal post-Brexit, after Theresa May revealed her “deep concern” about plans to impose tariffs on steel and aluminium imports to the United States.
In a phone call with Donald Trump on Sunday afternoon, the prime minister reacted to a series of tweets sent by the president attacking “very stupid” trade deals.
Trump has said he plans to slap a 25% tariff on steel imports and 10% on aluminium next week.
The government is hopeful of securing a “mutually beneficial” trade deal to help bolster the UK post-March 2019 - when Britain will exit the European Union.
But there are a few crucial reasons why it may not be plain sailing ahead.
1. Aviation offer
American negotiators have offered Britain a worse “open skies” deal after Brexit than the one it has as an EU member, according to the Financial Times.
The paper reported this week on secret formal talks on a new air services deal held in January, with the aim of plugging the gap when the UK leaves the EU-US open skies treaty.
The UK was offered a standard bilateral agreement - which experts say would be problematic for major airlines, including British Airways and Virgin, who have large foreign shareholders.
Chancellor Philip Hammond has previously warned flights could “theoretically be grounded” after Brexit if no aviation agreement is reached.
2. Chlorine chicken
UK farmers say they are worried about lower food standards should the two countries strike a deal.
Research by Sustain, the food and farming alliance, revealed US farmers and meat processors routinely use antibiotics, chlorine rinses and irradiation to reduce food-poisoning bugs in meat.
The issue of chlorinated chicken in particular has split Theresa May’s cabinet - with Defra secretary Michael Gove vehemently opposed to the practice and international trade secretary Liam Fox accusing the British media of being “obsessed” with the issue.
3. NHS fears
Theresa May sparked concern over the future of the NHS last month, when she refused to rule out the health service being included in any future trade deal.
During Prime Minister’s Questions, May was asked if she could give an “absolute guarantee” the NHS would not be on the table in future trade negotiations with Washington - just days after Trump claimed the system was “not working”.
The PM did not make a promise in her answers, and a Downing Street spokesman later said the government does not have an “existing position” on whether to allow US companies to run parts of the service.
Labour leader Jeremy Corbyn accused the government of “a race to the bottom” on standards and regulations.
4. Car trouble
Along with his steel tariff threat, Trump has also floated the idea of “applying tax” on cars imported to the US from the EU.
British manufacturers have already warned they could be unable to use a post-Brexit American deal because the industry is too tightly linked with EU suppliers.
Many US deals insist that most of a car’s parts are made domestically - which would leave Sunderland’s Nissan plant - and its 7,000 employees - out in the cold.
The head of Vauxhall, which employs 4,500 UK staff across two plants, also warned this week that a “lack of clarity” was putting future jobs at risk.
5. General tensions
Trump’s general tense relationship with Britain could sound the death knell for any future trade deal at all, some critics believe.
Sir Nigel Sheinwald, a former British ambassador to Washington, warned earlier this year that interventions by the US president in British issues - including his criticism of the NHS - makes the prospect of a swift transatlantic deal more remote.
According to a poll by the Observer, nearly three quarters of UK voters believe Trump is a risk to international stability.
And although Downing Street remains committed to the prospect of a future state visit by the president, two in five voters believe he should not be coming to the UK at all.
James McGrory, executive director at pro-Europe pressure group Open Britain, told HuffPost UK: “The government seems determined to go crawling cap-in-hand to Donald Trump in desperate pursuit of a free trade deal that they hope will bail them out of the economic damage of Brexit.
“But a trade deal with the US won’t come close to compensating for the costs. And there are already many signs that this won’t be as easy as they like to pretend.”
McGrory, a former adviser to ex-Lib Dem leader Nick Clegg, said the idea of the UK securing a “sweetheart deal” was “ludicrous”.
“Even if we do start negotiating such a deal, the likely requirements will be a lowering of our food standards to allow imports of chlorinated chicken, hormone-injected beef and milk from infected cows, not to mention the opening up of our NHS to US privatisation,” he added.
“No-one voted for Brexit just so we could cosy up to a US President who isn’t the least bit concerned about the best interests of our country. If that’s the cost of Brexit, we are all entitled to keep an open mind about whether it’s the right path.”