Prime Minister Boris Johnson will hold talks on post-Brexit trade with the top US diplomat on Thursday, eve of Britain's historic departure from the European Union.
The British premier will aim to paper over recent disagreements as he hosts US Secretary of State Mike Pompeo the day before nearly half a century of EU membership ends late Friday.
With Britain at a historic crossroads, Johnson wants to strike post-Brexit trade deals with both the bloc and the US, but has seen recent strains in the so-called "special relationship" with Washington.
Britain will enter a new chapter when it becomes the first country to quit the EU's institutions at midnight Brussels time (2300 GMT) on Friday.
Although it will remain under most EU rules during an 11-month transition period, Britain is then likely to lose privileged access to the single European market -- the world's largest and most important for UK trade.
But Johnson has argued he will negotiate an ambitious free trade agreement with his 27 former partners while also striking a lucrative trade deal with the US.
"It is a great moment for our country... a moment of hope and opportunity," the British leader said Wednesday, as he prepares to address the nation at 2200 GMT Friday -- an hour before Brexit.
Pompeo, in London on the first leg of a five-nation tour that also takes in Ukraine, sounded a positive note on arrival Wednesday.
"The #UK is an indispensable ally on a range of issues," he tweeted, adding the special relationship was being strengthened "through constructive discussions".
En route, he had told reporters Britain's decision to ignore months of US warnings and give China's Huawei tech giant a role in the rollout of its 5G network was "something we'll have a conversation about".
"We will make sure that when American information passes across a network we are confident that that network is a trusted one," he added.
Pompeo will also speak at a conservative think tank alongside Foreign Secretary Dominic Raab.
He met his British counterpart on Wednesday evening, with several contentious issues on the agenda.
Britain has been angered by Washington's refusal to extradite the wife of a US diplomat who is using the cover of diplomatic immunity to avoid prosecution over the death of a teenager in a road accident in England.
Meanwhile Johnson has defied expectations since taking power and failed to side with the US on everything from Huawei to the Iran nuclear deal that the US has abandoned.
President Donald Trump -- a long-time fan of Brexit and Johnson's ability to deliver it successfully -- has publicly urged Britain to rethink, yet has so far been restrained in his criticism.
But others, including Republican senators who will have to sign off on a future US-UK trade deal, have cautioned that sharing intelligence and striking an agreement could be imperilled by the Huawei decision in particular.
Johnson's hopes for a US trade deal are also complicated by Trump's unpopularity in Britain and domestic pressure to stand up to Washington.
Britons narrowly backed departing the EU in a 2016 referendum that left the country locked in political crisis and acrimonious division.
Johnson, who headed the pro-Leave campaign and became premier in July, won a thumping election victory in December on the mantra "get Brexit done".
That is now finally happening, with Britain's departure set in European law Wednesday, amid emotional scenes, as the bloc's parliament voted to ratify the divorce papers.
"We will always love you and we will never be far," said EU Commission president Ursula von der Leyen, adding: "Long live Europe."
Following the vote, MEPs burst into a chorus of "Auld Lang Syne", a traditional Scottish song of farewell.
Britain's eurosceptic lawmakers were in triumphant mood after two decades as a thorn in Brussels' side, brandishing British flags in contravention of the chamber's rules.