Theresa May will call for a "renewed" special relationship between Britain and America as she becomes the first world leader to meet Donald Trump since his inauguration as president last week.
Arriving in America on Thursday ahead of Friday's meeting in the White House, the Prime Minister will say that both the UK and US are undergoing a renewal which will allow them to "rediscover our confidence together" and "lead together again" in the world.
Downing Street hopes that the Oval Office meeting will allow Mrs May to establish the basis for a "strong and productive working relationship" with Mr Trump and agree a shared ambition to sign a UK-US free trade deal once Britain has left the EU.
But the PM has been urged to show caution in her dealings with the new President over issues ranging from trade and the environment to his campaign promises to sanction the use of waterboarding on terror suspects.
As a draft executive order suggested that Trump was preparing to order a review of interrogation methods for terror suspects and the possible reopening of "black site" prisons outside the US as well as the continued incarceration of "enemy combatants" in Guantanamo Bay, Mrs May assured the House of Commons that "we do not sanction torture, we do not get involved with that and that will continue to be our position".
The PM's official spokeswoman said that Mrs May recognised there would be "issues where we differ in approach and view with President Trump" and believed a close relationship would allow her to "raise these frankly and directly with the President". But she declined to say whether the use of torture would be on the agenda on Friday.
Firmly on the agenda will be Mrs May's desire to renew the special relationship, which she will say has played a vital role in creating the institutions and liberties of the modern world.
Speaking to Republican congressmen at their annual retreat in Philadelphia on Thursday, the PM will say: "The leadership provided by our two countries through the special relationship has done more than win wars and overcome adversity. It made the modern world.
"The institutions upon which that world relies were so often conceived or inspired by our two nations working together.
"It is through our actions over many years, working together to defeat evil or to open up the world, that we have been able to fulfil the promise of those who first spoke of the special nature of the relationship between us. The promise of freedom, liberty and the rights of man."
And she will tell the congressmen that withdrawal from the EU will give the UK "the opportunity to reassert our belief in a confident, sovereign and Global Britain, ready to build relationships with old friends and new allies alike".
Apparently linking the Brexit vote with Mr Trump's election, she will say: "As we rediscover our confidence together – as you renew your nation just as we renew ours – we have the opportunity, indeed the responsibility, to renew the special relationship for this new age. We have the opportunity to lead together again."
Mrs May is expected to hold private meetings with senior Republicans in Philadelphia before flying on to Washington DC for her face-to-face talks with Mr Trump, which follow an invitation from the President when the pair spoke by phone shortly after his election victory.
Downing Street will be hoping that the event will draw a line under the diplomatic tension caused when former Ukip leader Nigel Farage became the first UK politician to meet Mr Trump just days after his triumph over Hillary Clinton.
As well as trade, the PM is expected to set out her belief in the need for US-UK co-operation on issues ranging from Nato and counter-terrorism to creating the conditions for peace in Syria. And she will lay a wreath at Arlington Cemetery, which is the resting place of a number of British troops who died fighting alongside US forces.
During Prime Minister's Questions on the eve of her departure, former Labour leader Ed Miliband urged her to tell Mr Trump to abide by the terms of the Paris Agreement on climate change, while the Scottish National Party's Westminster leader Angus Robertson urged her not to make sacrifices on privatisation of healthcare or food safety to secure a trade deal with the US.
Senior Conservative Andrew Tyrie said the President had made clear on the campaign trail that he was ready to use torture "as an instrument of policy" and urged Mrs May to tell him that "in no circumstances will she permit Britain to be dragged into facilitating that torture, as we were after September 11".
Amnesty International UK director Kate Allen said: "As we saw with protests around the world last weekend, there is widespread fear of an erosion for human rights in and by the USA.
"Mrs May mustn't flinch from telling the President some basic truths about the complete unacceptability of keeping Guantanamo open or of authorising a return to the use of waterboarding and other torture."