Snazzy new US Embassy in London unveiled with 'indoor Grand Canyon'

US ambassador says the $1bn building is both welcoming and secure

The most surprising aspect of the pricey new US Embassy in London is what isn't there: a perimeter fence.

There is no imposing security barrier to protect the highly visible embassy in a city that has this year been targeted repeatedly by extremists.

Instead there are some public gardens with benches on the edge of the property, then a pond to keep unauthorised people from approaching the new building south of the River Thames. Officials are quick to emphasise the pond is not a moat, it does not encircle the entire building.

US ambassador Robert "Woody" Johnson said on Wednesday the US$1 billion building that opens to the public on January 16 is designed to be both welcoming and secure.

He said he hopes president Donald Trump will come to London for its official dedication, which may come weeks or longer after the embassy's first day of business.

"We are looking forward to welcoming the president when he comes over here," Mr Johnson told reporters during an advance look at the new facility in the Nine Elms neighbourhood. "I think he will be very impressed with this building and the people who occupy it."

He said the president's schedule is difficult and it's not clear when he will visit. Mr Trump has accepted an invitation for a state visit to be hosted by Queen Elizabeth II, but no date has been set.

British lawmakers and others have protested hosting Trump for a number of reasons, and some lawmakers have called for him to be banned from the UK.

The ambassador touted the new embassy as a technological marvel, but his remarks were at times drowned out by feedback from a faulty microphone.

The new building, which replaces the former US Embassy on Grosvenor Square in the heart of London, is playing a central role in the rejuvenation of the Nine Elms neighbourhood, which has seen a spurt in housing and office development.

Officials say it would have been prohibitively expensive to renovate the Grosvenor Square embassy, which opened in 1960, and update it with modern security features.

The new building, with its distinctive cube shape, is nearly twice as large as the Grosvenor Square facility. It is the single most expensive embassy building ever built by the United States, ambassador William Moser said, even though US diplomatic compounds in Kabul, Afghanistan and Baghdad, Iraq cost more.

Mr Moser, who supervises overseas building construction for the State Department, said the money for the site and its development was generated by selling other US government properties in Britain.

"It was built with no taxpayer dollars," he said.

The 12-story building offers a commanding view of the Thames and its design emphasises sustainability, including the use of water runoff to form a waterfall.

A number of interior gardens emphasise American themes — one evokes the Grand Canyon, another is designed to look like Pacific forests — and the housing for US Marines includes a landscaped outdoor seating area.

Architect James Timberlake says the new building exceeds security requirements without making the embassy look forbidding.

"It does so discretely rather than overtly," he said.