U.S. President Donald Trump cancelled a trip to London scheduled for next month to open a new embassy, saying he did not want to endorse what he understood was an Obama-era decision to move out of the old one.

The cancellation is a further blow to relations between the allies. More than a year into his presidency, Trump has yet to visit London, with many Britons vowing to protest against a man they see as crude, volatile and opposed to their values on a range of issues.

"[The] reason I canceled my trip to London is that I am not a big fan of the Obama Administration having sold perhaps the best located and finest embassy in London for 'peanuts,' only to build a new one in an off location for 1.2 billion dollars," Trump said in a tweet late on Thursday.

"Bad deal. Wanted me to cut ribbon-NO!" Trump said.

Trump, left, cancelled a trip to London set for next month to open a new embassy, saying he did not want to endorse what he understood was an Obama-era decision to move out of the old one. He has had tense exchanges with London Mayor Sadiq Khan, right, dating back to December 2015. (Jonathan Ernst & Clodagh Kilcoyne/Reuters)

While Trump cast it as solely his decision, his reception figured to be controversial after he retweeted videos from a far-right British group, and criticized London Mayor Sadiq Khan following a terror attack last year.

Khan's predecessor as mayor, current Foreign Secretary Boris Johnson, criticized both him and Labour Party Leader Jeremy Corbyn for discouraging the U.S. leader from coming to London.

"The US is the biggest single investor in the UK – yet Khan & Corbyn seem determined to put this crucial relationship at risk," Johnson said in a tweet. "We will not allow US-UK relations to be endangered by some puffed up pompous popinjay in City Hall."

The US is the biggest single investor in the UK - yet Khan & Corbyn seem determined to put this crucial relationship at risk. We will not allow US-UK relations to be endangered by some puffed up pompous popinjay in City Hall. —@BorisJohnson

Khan was unmoved by the development.

"Many Londoners have made it clear that Donald Trump is not welcome here while he is pursuing such a divisive agenda," the mayor said in a statement, about two hours before Johnson's tweet. "It seems he's finally got the message."

The decision to acquire a new London embassy site on the south bank of the Thames was announced in 2008 under George W. Bush along with the plans to put the old Grosvenor Square site in upscale Mayfair up for sale.

Many Londoners have made it clear that Donald Trump is not welcome here while he is pursuing such a divisive agenda. It seems he’s finally got that message. <a href="https://t.co/YD0ZHuWtr3">pic.twitter.com/YD0ZHuWtr3</a> —@SadiqKhan

A pillar of Britain's foreign policy since World War Two, the so-called "special relationship" with Washington has taken on added importance as Britain prepares to leave the European Union in 2019 and seeks new major trade deals.

Prime Minister Theresa May was the first foreign leader to visit Trump after his inauguration in January last year, and they were filmed emerging from the White House holding hands. She later said Trump took her hand in a gentlemanly gesture as they walked down a ramp.

But British officials have been dismayed by some of Trump's pronouncements, particularly a proposed ban on Muslims entering the United States and most recently when Trump rebuked May on Twitter after she criticised him for retweeting British far-right anti-Islam videos.

Security concerns about embassy site

During May's U.S. trip a year ago, she extended an invitation to Trump to make a formal state visit that includes pomp, pageantry and a banquet with Queen Elizabeth.

May's spokesperson told reporters Trump was welcome in London and that the invitation to visit had been accepted, although no date agreed. He said the opening of the embassy was a matter for the U.S. government.

"The U.S. is one of our oldest and most valued allies and our strong and deep partnership will endure," the spokesperson said.

The U.S. Embassy in Grosvenor Square is shown in central London in 2008, the year it was announced it would be relocated from London's tony Mayfair district to south of the River Thames. (Alastair Grant/Associated Press)

The American flag was this month removed from Grosvenor Square, where the U.S. Embassy has been based since 1938 with the area known as "Little America" during the Second World War, when the square also housed the military headquarters of Gen. Dwight D. Eisenhower.

In October 2008, the embassy was put up for sale and was sold the following year to Gulf investor Qatari Diar. The purchase price was not disclosed. In 2009, it was given "listed" status, which limits changes that can be made to the building's exterior because of its historical significance.

Woody Johnson, Trump's appointed U.S. ambassador to Britain, told reporters last month that moving to the new site at Nine Elms reflected "the global outlook of the U.S. going forward in the 21st century: rather looking out, than looking in."

"This isn't just a new office, though. It signifies a new era of friendship between out two countries. President Trump wants us to work more closely than ever with the UK," said Johnson. He said he hoped the president would attend the opening ceremony.

There had long been security concerns about the Grosvenor Square site, dating back to the late 1990s after attacks on U.S. embassies in Africa.

Some local residents had opposed measures that they felt would detract from one of London's plushest neighbourhoods, while others feared not enough was being done to ensure they would not be caught up in any attack.

The new embassy is a veritable fortress set back at least 30 metres from surrounding buildings — mostly newly erected high-rise residential blocks — and incorporating living quarters for U.S. marines permanently stationed inside.