John Bolton, the national security adviser to Donald Trump and one of the pre-eminent advocates of “America first”, could not have been more solicitous to the Boris Johnson government – but his overtures may come with a sting in the tail for the UK.

The messages of solidarity poured out. We are with you, he vowed, saying Brexit was in the US national security interest, with or without a deal with the EU by 31 October. Laced with a few barbs at the expense of Brussels, he presented his credentials as a pioneer Brexiter, arguing he was a leaver before there were leavers.

But Bolton did not just vow friendship or repeat the oft-made promise that the UK will be at the front of the queue for any trade deal: he came with a specific proposal.

Britain and the US could strike interim deals lowering trade barriers in specific areas, such as manufacturing, before a comprehensive trade deal could be signed some years down the line, he said. He was sure such deals could be greeted with unanimous bipartisan support by Congress, the body that sanctions US trade agreements. Some doubt the possibility of striking deals before everything is agreed, however.

The aim is to provide the UK with a safety net as it loses access to European markets in a no-deal scenario. It is not quite a bailout, but it underlines how much the Trump administration sees Britain’s exit from the EU as being in the US’s national security interest.

Boltonians have always seen the EU as not just a bureaucratic behemoth or potential rival to US power but an affront to how it believes the world should be ordered. The traditional US argument that Britain inside the EU can act as an influential advocate for Washington’s interests has been jettisoned in the Trump era.

Multilateral power blocs need to be neutered and, as Trump argued in his speech to the UN in 2018, the “doctrine of patriotism” must hold sway. “Around the world, responsible nations must defend against threats to sovereignty not just from global governance, but also from other, new forms of coercion and domination,” he told the general assembly. The US, he said, will always choose independence and cooperation over global governance.

It is quite clear that if Bolton had his way, Brexit would not just liberate Britain but lead to a wider breakup of the EU. It was notable that the only Conservatives he planned to meet outside government on his visit were leading figures in the European Research group such as Bernard Jenkin, Iain Duncan Smith and Bill Cash, not exactly a representative cross-section of the Tory benches.

In championing US support for Brexit, Bolton brushed aside many of the problems of a no-deal exit or US-UK trade deal. No deal represented no risk to the Good Friday agreement, he asserted.

He said he had asked for the threat a US trade deal could pose to the NHS to be explained to him and he had not understood the argument, so he would not comment. Concern about chlorinated chicken being sold to UK consumers was treated largely as a joke. The other side of an argument is not somewhere Bolton often frequents.

But the bigger picture is the extent to which the UK outside the EU will feel required to come under Washington’s sway. Bolton said he respected the UK’s short-term need to focus on Brexit, but he laid down markers on the two issues that most concern the US: the role of the Chinese technology company Huawei in the UK’s 5G network and the future of the Iran nuclear deal.

On the former he claimed the UK had agreed to reconsider from first principles, an analysis not shared by UK officials. On Iran, Bolton was content to bide his time, possibly believing the deal will collapse anyway, but took note that the Johnson team had already ditched plans for a separate European maritime security operation in the Gulf and would instead come under the umbrella of the US-led Operation Sentinel.

But for the Foreign Office to abandon the nuclear deal now would represent such a complete about-face that one imagines senior diplomats would resign. The 2015 deal, brokered by the EU and Obama administration, is seen as one of the great diplomatic achievements of this century, and for Britain to join in Trump’s wilful destruction of it would be seen as an act of obeisance to Washington. It would also infuriate Berlin and Paris, who still think the deal can be rescued.

That does not mean the deal will survive. The relentless economic pressure from the US is forcing Tehran to take steps that the UK cannot defend. The forthcoming G7 summit in Biarritz is where some of these issues will likely be played out. It may also be where Johnson finds out the true extent to which Washington wants to pull London away not only from the European Union, but from European values.