The prime minister has hailed the president's visit as an opportunity to boost UK-US trade post-Brexit and to strengthen co-operation on security and anti-terrorism.
But the threat of mass protests and demonstrations has prompted the biggest police operation since the 2011 riots, with nearly every force in England and Wales contributing officers.
The PM's pledge came after Mr Trump said the UK was in "turmoil", that meeting Vladimir Putin would be the "easiest" part of his European trip and that he wanted to meet his "friend" Boris Johnson.
Undeterred by this apparent snub, Mrs May declared: "When we leave the European Union we will begin to chart a new course for Britain in the world and our global alliances will be stronger than ever.
"There is no stronger alliance than that of our special relationship with the US and there will be no alliance more important in the years ahead."
She said: "The UK and the US already have a uniquely close partnership in the fight for democracy and global security and we share a global outlook across the vast majority of foreign policy issues.
"Our trade and investment relationship is unrivalled - we are the largest investors in each other's economies and every day a million British people go to work for US companies in the UK and a million Americans go to work for UK companies in the US."
And she added: "This week we have an opportunity to deepen this unique trading relationship and begin discussions about how we will forge a strengthened, ambitious and future-proof trade partnership.
"As two nations - we are safer, more prosperous and more creative when we work together and I am looking forward to this week's important discussions."
Downing Street has revealed that the talks between the two leaders at Chequers, which will also be attended by the new Foreign Secretary Jeremy Hunt, will be dominated by Russia, trade, Brexit and the Middle East.
The Chequers talks, on Friday morning, come just days before the president heads to Helsinki for a summit with Vladimir Putin which western diplomats fear could weaken NATO's anti-Russia strategy.
There is also anxiety in Whitehall that Mr Trump could make outspoken comments on Brexit during his UK visit which would undermine the PM's Chequers agreement and embolden rebel Tory MPs.
Revealing the government's determination to put trade at the forefront of the agenda, the president and wife Melania will be greeted when Air Force One touches down on Thursday afternoon by International Trade Secretary Liam Fox.
The first big set-piece event during the president's visit is a lavish black tie dinner at Blenheim Palace in Oxfordshire, birthplace of Sir Winston Churchill, attended by senior cabinet ministers and bosses of top UK and US companies.
The teetotal president - whose alcoholic brother died at 43 - will be offered a menu of Scottish salmon, Hereford beef and vegetables and strawberries and clotted cream ice cream.
Besides the PM, who is hosting the dinner, Mr Hunt, Dr Fox, Chancellor Philip Hammond, Cabinet Office minister David Lidington, Business Secretary Greg Clark, Foreign Office minister Sir Alan Duncan and Transport Secretary Chris Grayling, who chairs the British-American Parliamentary Group, will be attending.
US companies represented at the dinner will include the private equity group Blackstone and the asset management firm Black Rock, which pays former chancellor George Osborne £650,000 for a four-day week.
From the UK, bosses attending will include those from the drinks giant Diageo and the project management company Arup.
After spending the night at the US ambassador's residence, Winfield House, in London's Regent's Park, the president will join the PM and Defence Secretary Gavin Williamson visiting what Number 10 calls "a demonstration of the UK's cutting edge military capabilities and integrated UK-US military training" by members of the special forces.
After the Chequers talks, the lunch menu there will be Dover sole, Chiltern lamb and vegetables and lemon meringue.
Mr Trump will then meet up again with Melania and they will take tea with the Queen at Windsor Castle.
While the president is on his military visit and holding talks with the prime minister at Chequers, Melania will be taken by the PM's husband Philip on a visit in London to meet veterans and then schoolchildren.
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Later the Trumps will fly to Scotland, where Air Force One will be greeted by the Scotland Secretary David Mundell and not the First Minister Nicola Sturgeon, ahead of a golf weekend at his Turnberry resort in Ayrshire.
It is thought his playing partners on the course will include golf fanatic Prince Andrew and possibly a top professional, such as Rory McIlroy, who played with Mr Trump at the president's course in Florida last year.