LONDON (BLOOMBERG) - British Prime Minister Boris Johnson will land in the US this week on his first trip outside of Europe since the start of the pandemic, with his most critical relationship - that with President Joe Biden - at a delicate juncture.
A three-way deal to supply nuclear submarines to Australia announced this week has reinforced the idea of a special bond, underpinned by US-Britain security interests, even though the two men have not always seen eye to eye.
Mr Johnson now has a number of other tricky topics with which he needs help from the United States, including the crisis in Afghanistan and, especially, how to accelerate momentum behind a stumbling global environmental summit that Britain will host next month.
On Monday (Sept 20), the Prime Minister will use a breakout meeting at the United Nations General Assembly in New York to urge wealthy nations to stump up more cash to fight climate change.
He will then head to Washington for a meeting with Mr Biden that will come under close scrutiny - not only because of the British media's obsession with the "special relationship" immortalised by Ms Margaret Thatcher and Mr Ronald Reagan in the 1980s.
There is also the ghost of Mr Donald Trump, who openly admired Mr Johnson but humiliated his predecessor Theresa May.
Mr Johnson's relationship with Mr Biden has so far been more awkward. He was rebuked by the President for endangering the Northern Ireland peace process with his approach to Brexit, and meaningful negotiations on a trade deal have yet to begin. Meanwhile, Britain was left blindsided by the US handling of the chaotic exit from Afghanistan amid little consultation with Nato allies.
With few opportunities for face-to-face meetings during the pandemic, the Conservative British leader has been unable to deploy his famous charm to win round the Democrat in the White House.
What is clear is that close ties to the relatively new president and his team cannot be taken for granted, in spite of the history binding the two nations and Mr Biden's promise to international allies after taking office that "America is back".
In Afghanistan, for example, Mr Biden rejected calls from Britain, among others, to delay the pullout of troops. And British officials have struggled to shift the Biden administration's scepticism over Brexit.
Yet the US seems more aligned with Britain over China than other European nations, a position underlined by the tightly held secret that Australia was going to ditch France and attach itself to Mr Biden and Britain in getting new submarines equipped with nuclear technology.
An angry France responded by pulling its US envoy to Washington for the first time ever after being blindsided by the pact Mr Biden, Mr Johnson and Australian Prime Minister Scott Morrison discussed at the Group of Seven (G-7) summit in England in June.
And France is peeved at Britain, too, accusing its neighbour and trade partner of opportunism and denigrating Britain as "spare tyre" in the submarine deal.
In an interview with France 2 on Saturday, French Foreign Minister Jean-Yves Le Drian also warned of potential consequences for the Nato military alliance.
In all this, Mr Johnson must still tread carefully with Mr Biden; there is little sign of progress on his prized post-Brexit trade deal with Washington, while in the short term, he needs the President's support to secure more ambitious global climate pledges at the COP26 round of United Nations talks in Glasgow starting late October.
Both leaders spoke at a virtual meeting on Friday convened by the US President on climate change, with Mr Biden calling for nations to bring their "highest possible ambitions" to the Glasgow summit.
Britain is focused on delivering on the promise made at the 2009 summit in Copenhagen, and renewed in Paris in 2015, that poorer nations were to receive US$100 billion per year from 2020 to help them cut carbon emissions. But wealthy nations are stalling in their efforts.
"World leaders have a small window of time left to deliver on their climate commitments ahead of COP26," Mr Johnson said in a statement ahead of his trip. "My message to those I meet this week will be clear: Future generations will judge us based on what we achieve in the coming months."
Mr Biden's stance will be critical to persuading others to follow suit, which is why Mr Johnson's mission is a delicate one and will rely on powers of persuasion.
But he has fallen short before in negotiations on climate change: At the G-7 meeting in June, a deal to end domestic coal use in G-7 economies was scuppered over US nervousness about the impact on domestic politics.
During those talks, he was working on the submarine alliance during private meetings. This week, he will get a sense of how far that deal has helped to cement this crucial relationship.