The new US embassy in London is located in a former post-industrial wasteland on the south side of the River Thames -- a world away from its historic home in the capital's luxurious Mayfair district.

Announcing on Friday that he would not come for the embassy's inauguration, US President Donald Trump said it was in an "off location" and that the former embassy had been sold to Qatar for "peanuts".

While Republican Trump put the blame on his Democrat predecessor Barack Obama, the decision to move from Mayfair to Nine Elms was in fact taken by the administration of Republican former president George W. Bush in 2008.

It followed the 1998 US embassy bombings in Tanzania and Kenya and the September 11, 2001 attacks in the United States, which made security considerations paramount.

The most striking feature of the new embassy is a half-moon shaped moat surrounding it, which gives the 12-storey cube building a fortress-like feel.

It has had its share of critics even before Trump.

"Those desperate to find a symbol of the current American administration in the new embassy in Nine Elms will find one all too easily: it is a squat, fortified cube inside a moat," The Economist magazine wrote.

Peter Rees, the City of London's former head of planning, was quoted by The New York Times newspaper as saying that it was "like moving from New York's Upper East Side to New Jersey".

Trump said the building cost $1.2 billion (990 million euros) -- a price tag that reportedly makes it the most expensive embassy building in the world.

Architects KieranTimberlake, based in the US city of Philadelphia, were selected to build it in 2010.

- 'Centre stage' -

The new embassy is located in a formerly rundown area now seeing vast construction projects where there were once warehouses and railyards.

Asked whether British Prime Minister Theresa May shared Trump's views about the area, her spokesman on Friday said it was "a vibrant and important part of London".

Ravi Govindia, leader of Wandsworth Council, the borough where the area is located, rejected Trump's comments about being "off location".

"It is certainly centre stage today," he said.

Govindia called it an "iconic new zone", pointing out that Apple were moving their offices to the area.

He said a £15-billion ($20.5 billion, 17 billion euro) regeneration of the area would bring 20,000 new homes and 25,000 permanent jobs.

The Dutch embassy is also planning to move to the area and luxury apartment buildings are sprouting up, including one which will have a glass-bottomed swimming pool spanning a void between two towers.

- 'Wear and tear' -

Embassy staff have gradually been transferred to the new building in recent months and it is due to open officially for consular services next week.

The US flag was lowered for the final time on Tuesday from the top of the former 600-room embassy in Grosvenor Square, where US General Dwight Eisenhower had his headquarters during World War II.

The area became known as "Little America" at the time.

Current ambassador Woody Johnson, a Trump appointee who owns the New York Jets American football team, called the lowering of the flag "a poignant moment".

The modernist embassy building by Finnish-American architect Eero Saarinen was completed in 1957 and sold in 2009 to Qatari Diar, the real estate investment arm of Qatar's governme nt.

The price tag for the deal was never disclosed and Qatari Diar plans to turn it into a luxury hotel.

At the time of the selection, then ambassador Louis Susman said the old building was "over-crowded, does not meet modern office needs and required security standards" and was showing "wear and tear".

Asked about the prospect of Trump's visit, current ambassador Johnson said he was looking forward to it, adding: "I think he will be very impressed with this building and the people who occupy it."

He said the new embassy was a "signal to the world that this special relationship that we have is stronger and is going to grow and get better".