The US President caused a stir earlier this month when he announced that he would not after all be visiting the UK to open the new embassy in Vauxhall, tweeting that it was in an “off location”.
He has subsequently returned to the subject yesterday, claiming the building “came out tremendously over budget”.
He said: “So now we have an embassy that cost $1.2billion, I think it was much more than that… in the wrong location.”
At the time, his claims raised eyebrows, with many suggesting he was ducking out of the visit to avoid the risk of widespread protests from those angry at the US President’s comments on immigration, race and a wide range of other subjects.
However, Mr Tillerson, who was speaking to reporters while flying back to Washington following a trip to the west coast yesterday, suggested an altogether different reason.

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He said: “I mean, we still have the special relationship with the British people.
“As you know, President Trump was supportive of the UK’s exit from the EU. He still thinks that was the right decision for them.
“Britain needs to focus on those Brexit negotiations right now, which is really important to them, and I think the President realises that’s where Prime Minister May really needs to focus her attention.”
While the deal was concluded under President Barack Obama, the original decision to move the embassy from Grosvenor Square in upmarket Mayfair to the south bank of the Thames was actually agreed in 2008 under President George W Bush, who, like Mr Trump, represented the Republican party.
When pressed as to whether he agreed with Mr Trump’s claim that it was a mistake to build the embassy on the south of the river Thames, Mr Tillerson said: “That’s a decision that’s already been taken, so I don’t think we need to revisit it.”
Nevertheless, he added: “We don’t have the details yet, but I hope to get by the embassy.”
The cancellation of Mr Trump’s trip has been seen in some quarters as a further blow to relations between Britain and the United States.
More than a year into his presidency, Mr Trump has yet to visit London, with many Britons vowing to protest against the US President.
He is due to be afforded the honour of a state visit next year, with Mrs May flying to Washington just days after his election to deliver the invitation.
However, no details have been announced and such an event would likely also attract high-profile demonstrations.