Boris Johnson will be warned by Joe Biden not to put peace in Northern Ireland at risk, as the UK heads for a Brexit trade war with the EU over sausages.

In their first face-to-face meeting, ahead of the G7 summit in Cornwall, the prime minister and the US president will launch a new bid to reopen US/UK air links as they seek to revive the close ties of wartime leaders Winston Churchill and Franklin Roosevelt with an updated Atlantic Charter.

But the White House made clear that Mr Biden will voice his concern over London’s threat of a further breach of the Northern Ireland protocol agreed by Mr Johnson in 2019.

European Commission vice-president Maros Sefcovic warned on Wednesday that “patience is wearing very, very thin” in Brussels, which is ready to slap tariffs and quotas on exports if the UK presses ahead with an extension of a “grace period” on chilled meat exports to get round EU hygiene rules.

The row is the last thing Mr Biden wants on his first international trip as president, which he says he will use to demonstrate to China and Russia that “Europe and the United States are tight” in the wake of the divisions of the Trump years.

US national security adviser Jake Sullivan said the president’s trip – also taking in talks with Nato and the EU in Brussels and an encounter with Russia’s Vladimir Putin in Geneva – will “advance the fundamental thrust of Joe Biden’s foreign policy to rally the world’s democracies to tackle the great challenges of our time”.

And on the UK’s stand-off with Brussels over Northern Ireland, he said: “Whatever way they find to proceed must, at its core, fundamentally protect the gains of the Good Friday Agreement and not imperil that. And that is the message that President Biden will send when he is in Cornwall.”

Adding to the pressure, it was reported last night that America’s most senior diplomat in Britain told Brexit minister Lord Frost that the UK government was “inflaming” tensions in Ireland and Europe with its opposition to Irish Sea border checks.

With the marching season drawing near, a senior UK source close to negotiations effectively accused the EU of putting peace at risk by adopting a “purist” approach to applying the protocol.

“It’s crucial not to give any room to violence or a sense that violence is any part of the solution to these problems,” said the source. “We need to show that normal politics can solve them and that’s why the purist approach is so risky.”

Mr Johnson insisted he was “not worried” that the threat of trade war will overshadow the three-day gathering of major democracies – the US, the UK, France, Germany, Italy, Canada, Japan and the EU – which he is hosting at the beach resort of Carbis Bay from Friday.

But he was warned that his chairmanship of the gathering is being undermined by his decision to slash UK aid funding from the 0.7 per cent of national income enshrined in law by David Cameron to 0.5 per cent.

The policy director of the International Rescue Committee, Daphne Jayasinghe, told The Independent: “Removal of the cut would be very much in line with the leadership that the UK government is promoting as part of its G7 presidency. The commitments that they are trying to mobilise among other G7 countries will really be undermined without that commitment to 0.7.”

With France committing to reach the United Nations’ 0.7 per cent target and Germany and the US increasing aid spending, the UK is “very much the outlier as the only G7 country at this summit making these kinds of cuts”, said Ms Jayasinghe, who added the impact was already being felt in the loss of clean water and sanitation for Rohingya refugees in Bangladesh and food aid for war-torn Yemen.

“The promise of ‘global Britain’ will really ring hollow unless it is matched with a commitment to funding and some certainty, which is sorely lacking at the moment,” said Ms Jayasinghe.

The UK travel industry gave a guarded welcome to Mr Biden and Mr Johnson’s expected agreement on a new travel taskforce, overseen by transport secretary Grant Shapps, to make recommendations on reopening flights as soon as possible.

Clive Wratten, CEO of the Business Travel Association, said: “Jobs won’t be saved, nor livelihoods protected, until we are given a certainty on dates for the resumption of international travel.”

And Virgin Atlantic CEO Shai Weiss said Mr Johnson should use the G7 to move the US onto the quarantine-free “green list” for UK travellers.

“The creation of the Atlantic Taskforce is positive recognition of the importance of the UK-US travel corridor and a first step towards reopening the skies,” said Mr Weiss. “But in the absence of a definitive timeframe, it again falls short of providing airlines, businesses and consumers with much-needed certainty.”

Direct transatlantic travel from the UK to the US has been banned for 15 months by a presidential proclamation inherited from Trump by Biden, while the US is on Britain’s “amber list”, requiring 10 days’ home quarantine.

Modelled on the historic joint statement made by Churchill and Roosevelt in 1941, setting out their goals for the post-war world and paving the way for the creation of the UN and Nato, the new Atlantic Charter is designed to demonstrate that the UK and the US share the same shared values in the modern world of cyberattacks, climate change and pandemic.

It marks a clear desire by Mr Biden to put firmly in the past his predecessor’s prickly and inward-looking stance towards traditional US allies.

And it reflects Mr Johnson’s desire to move on from the “special relationship” promoted by earlier prime ministers in a way which he is said to regard as “weak and needy”.

Mr Johnson said: “While Churchill and Roosevelt faced the question of how to help the world recover following a devastating war, today we have to reckon with a very different but no less intimidating challenge – how to build back better from the coronavirus pandemic.

“And as we do so, cooperation between the UK and US, the closest of partners and the greatest of allies, will be crucial for the future of the world’s stability and prosperity.

“The agreements President Biden and I will make today, rooted as they are in our shared values and outlook, will form the foundation of a sustainable global recovery. Eighty years ago the US president and British prime minister stood together promising a better future. Today we do the same.”

Shadow foreign secretary Lisa Nandy said Mr Johnson “must not squander this opportunity to reset the relationship with one of our most important international partners”.

She called on the PM to provide a “cast-iron guarantee of the UK government’s continued commitment to the Good Friday Agreement, and pledge to end the dangerous actions and rhetoric that have placed it under such strain”.

And she said he must “end the UK’s attempts to water down global tax reform” and match Mr Biden’s ambitions to create a fairer global tax system, with a global minimum corporation tax rate of 21 per cent rather than the 15 per cent trumpeted by the Treasury last week.

The two leaders are expected to agree to pursue a bilateral technology agreement on artificial intelligence and quantum technology as well as closer work on genomic sequencing and variant assessments.