DOWNING St has denied that Donald Trump refused a one-to-one meeting with Theresa May because she is an outgoing prime minister, who will soon be out of office.

As the US President began his three-day state visit, he immediately launched a Twitter tirade at Sadiq Khan, branding the London Mayor a "stone cold loser".

In return the mayor's office fired back, saying Mr Trump was offering "childish insults which should be beneath the President of the United States".

The spat came as Downing St released the President’s itinerary, which does not include a one-to-one meeting with Mrs May.

READ MORE: Politics Live: Donald Trump to begin 3-day state visit to UK

In contrast, it has been suggested Mr Trump will sit down and meet Boris Johnson, the former Foreign Secretary and bookies’ favourite to succeed the PM, and Nigel Farage, the leader of the Brexit Party, which won last week’s European elections across the UK.

Downing St, asked when Mrs May would have a one-to-one with the President, said this would come in the meeting of the UK and US delegations on Tuesday in the No 10 Cabinet Room. It stressed this was “always going to be the case”. The meeting will include Jeremy Hunt, the Foreign Secretary, and officials.

The PM’s spokesman said: “These are always how the discussions take place with any leader…There is nothing unusual here.”

He pointed out that on events like a tour of the Churchill War Rooms there would be discussions between “just the two of them”.

Asked directly if Mr Trump had declined to have a one-to-one meeting with the PM because she was on her way out, the spokesman replied: “I’m sure the answer to that is no.”

Previous occupants of No 10 and the White House have held private one-to-one talks before, including Tony Blair and George W Bush, whose meeting at the Crawford Ranch in the run-up to the Iraq War became the subject of intense focus after the conflict.

Asked how she reacted to the suggestion from the President that in the year since they met at Chequers, Mrs May had messed up Brexit by allowing Brussels to “have all the cards” in the negotiations, the spokesman said: “She worked as hard as she could to get the best possible deal for the UK.”

READ MORE: Donald Trump in Twitter blast at Sadiq Khan as he lands in UK for state visit

Downing St said Mrs May agreed with Mr Hunt and Matt Hancock, the Health Secretary, who stressed the NHS would be off limits in future post-Brexit trade talks.

Woody Johnson, the US ambassador to the UK, said at the weekend that he expected the "entire economy," including the health service, would be part of a future deal.

But Mr Hancock hit back at Mr Johnson's comments, saying the NHS was "not for sale".

"Yes, we'd love to make it cheaper to buy your life-saving pharmaceuticals but the NHS will not be on the table in any future trade talks," he tweeted.

The PM's spokesman said he expected the issue of a free trade agreement [FTA] to come up in the talks between the President and Mrs May.

"One of the issues you would expect the Prime Minister to raise is our economic partnership and how we can work together to strengthen ties and support our business," he said.

“You can expect us to discuss the future trading relationship; both the PM and the President have expressed their desire for an ambitious FTA once the UK leaves the EU," he added.

Today, after arriving at Stansted Airport, the state visit began with an official ceremonial welcome and guard of honour at Buckingham Palace with the Queen, Prince Charles and the Duchess of Cornwall. A royal gun salute was fired in Green Park and at the Tower of London.

This afternoon, Her Majesty will host a private lunch for Mr Trump and his wife, Melania, at Buckingham Palace, after which they will view a special exhibition from the royal collection with historical significance to the US.

The President and First Lady will visit Westminster Abbey with the Duke of York to lay a wreath at the Tomb of the Unknown Soldier and then travel to Clarence House for tea with Prince Charles and the Duchess of Cornwall.

This evening Mr Trump and his wife will attend a state banquet at Buckingham Palace, hosted by the Queen, who, together with the President will make speeches at the start of the meal.

Other ministers who will attend alongside Mrs May are: Mr Hunt; David Lidington, her de facto deputy; Philip Hammond, the Chancellor; Michael Gove, the Environment Secretary; Penny Mordaunt, the Defence Secretary; Liam Fox, the International Trade Secretary; Baroness Evans, the Leader of the House of Lords, and Sir Alan Duncan, the Minister for the Americas.

Jeremy Corbyn, the Labour leader, Ian Blackford, the SNP leader at Westminster, and Sir Vince Cable, the Liberal Democrat leader, have all refused to attend in protest at the red carpet treatment being afford the President. John Bercow, the Commons Leader, has also declined an invitation to attend.

Tomorrow, the PM and President will begin the day by co-hosting a round-table meeting for UK and US business leaders at St James’s Palace. This will also be attended by the Duke of York, Mr Hammond and Dr Fox.

READ MORE: In Pictures: Donald Trump’s state visit to the UK

Later, Mrs May and her husband Philip will greet Mr and Mrs Trump in Downing St. More pictures will be broadcast of the two couples in No 10’s White Room, which overlooks St James’s Park.

This will be followed by wider bilateral talks with the UK and US delegations in the Cabinet Room and then lunch in Downing St’s state dining room hosted by the PM.

After that, Mrs May and the President will hold a joint press conference at the Foreign Office.

While the latter events take place Mr May and Mrs Trump will host a party in No 10’s rose garden for staff and their families from the US embassy and Downing St.

Later, the PM and Mr Trump will have a private tour of the Churchill War Rooms in Whitehall accompanied by their spouses.

In the evening, the President will host a return dinner in the US ambassador’s residence in Regent’s Park.

On Wednesday, Mrs May will be in Portsmouth for events to commemorate the 75th anniversary of the D-Day landings. She will have a series of bilateral meetings with foreign leaders, some 15 of whom will be in attendance.

READ MORE: Donald Trump's UK State visit: What will the president do on his three-day UK trip?

The events will include testimonies from veterans, theatrical performances and live music. There will be fly-past of 24 aircraft, including the Red Arrows and WW2 spitfires.

The PM will among national leaders who will give readings during the ceremony. She will read a letter from Captain Norman Skinner of the Royal Army Service Corps, to his wife Gladys on June 3 1944, which was in his pocket when he landed on Sword Beach in Normandy on June 6. He was killed the following day leaving his wife and two young daughters.

After the ceremony, Mrs May and her counterparts will attend a reception with veterans, which will be followed by a lunch for the national leaders, hosted by the PM.

The Queen will then formally bid farewell to Mr and Mrs Trump in Portsmouth, marking the end of the state visit. They are due to travel on to Ireland for a short visit.

Later in the day, Mrs May will be aboard HMS Queen Elizabeth, the country’s new aircraft carrier, docked in Portsmouth for the commemoration, to watch as some 300 veterans set sail to Normandy, where on Thursday more D-Day commemorations will take place.

Early that day, the PM and her husband will attend the inauguration of a new British memorial to the British servicemen and women who died during the D-Day landings. Emmanuel Macron, the French President, will also be present. The memorial has been supported by £20 million from fines levied on the banking industry for manipulating the inter-bank LIBOR lending rate.

Later, Mr and Mrs May will attended a memorial service at Bayeux Cathedral alongside the Prince of Wales and the Duchess of Cornwall. This will be followed by a commemoration event at which the PM will lay a wreath and give a reading. Later, she and her husband will attend a lunch for veterans.