Donald Trump blamed Boris Johnson for his attempt to let Harry Dunn's distraught parents meet the US spy's wife accused of killing their son in a crash.
The US President had Anne Sacoolas, 42, waiting in an adjoining room as he held crunch talks with Charlotte Charles and Tim Dunn at the White House today.
But the grieving parents decided not to face Sacoolas, who they believe was responsible for the teenager's death after her car collided with his motorbike outside RAF Croughton in Northamptonshire in August.
And Mr Trump since claimed he was instructed by the UK Prime Minister.
"I spoke with Boris, he asked me if I'd do that, and I did it," Mr Trump said.
"She was in the room right out there, we met right here.
"I offered to bring the person in question in, and they weren't ready for it.
"Unfortunately they wanted to meet with her and unfortunately when we had everybody together they decided not to meet."
The showdown happened after Sacoolas was wrongly granted diplomatic immunity following the crash.
It is understood Mrs Sacoolas was driving on the wrong side of the road.
Mr Trump, 73, backed this belief in an astonishing press conference. He lamented how roads "are opposite" in Europe.
The world leader added: "I believe it was going down the wrong way because that happens in Europe.
"You go to Europe and the roads are opposite.
"It's very tough, if you're from the United States you do make that decision to make a right turn where you're supposed to make a left turn, the roads are opposite.
"She said that's what happened.
"That happens to a lot of people, by the way."
Sacoolas has said she is "disappointed" not to have met the family today.
A statement issued by Anne Sacoolas' lawyer Amy Jeffress said: "We are trying to handle the matter privately and look forward to hearing from the family or their representatives.
"Anne accepted the invitation to the White House with the hope that the family would meet and was disappointed."
