US presidential hopeful Mitt Romney's arrival in London for the Olympics was overshadowed on Thursday by a disputed remark to a Britsh newspaper and unflattering comments about the Games' build-up.

The Republican, a former governor of Massachusetts, jetted in with wife Ann on Wednesday for a three-day trip which will take in the opening ceremony and a meeting with Prime Minister David Cameron.

However, he left a storm of controversy after the Obama administration seized upon a reported remark by an aide that the president does not understand the "Anglo-Saxon heritage" shared by Britain and the United States.

The White House hopeful's campaign scrambled to deny that one of its operatives had told British newspaper the Daily Telegraph that Romney, unlike Obama, understands the "Anglo-Saxon heritage" underpinning the so-called special relationship with Britain.

Romney campaign spokeswoman Amanda Hennenberg said in a statement that the British report was mistaken.

"It's not true," she said. "If anyone said that, they weren't reflecting the views of governor Romney or anyone inside the campaign."

Senior Obama re-election strategist David Axelrod called the comments "stunningly offensive."

Romney also made undiplomatic remarks about Britain's Olympic preparations as final rehearsals were held for the ceremony which takes place on Friday.

"It's hard to know just how well it will turn out," Romney told NBC News from London.

"There are a few things that were disconcerting," he said.

"The stories about the private security firm not having enough people, the supposed strike of the immigration and customs officials -- that obviously is not something which is encouraging," he said.

British border officials on Wednesday called off a 24-hour walkout by immigration staff scheduled for Thursday, the eve of the opening ceremony.

Romney even called into question whether the British people as a whole were behind the spectacle, saying this would be key to their success.

"Do they come together and celebrate the Olympic moment? And that's something which we only find out once the Games actually begin," he said.

Romney's Olympic eye is keener than most. The multimillionaire former businessman and investor was called in to head the 2002 Winter Games in Salt Lake City after preparations were marred by scandal, and has first-hand knowledge of how to put on a successful Olympics.

Romney has a personal connection with the London Games. His wife Ann co-owns the horse Rafalca, which will compete in Olympic dressage.

While Ann Romney herself will not ride Rafalca in competition -- the horse's trainer Jan Ebeling will take the reins -- she said in June that competing in the Olympics was "a dream come true."

And yet her husband sounded on NBC like he knew little about competitive dressage, which in London marks its 100th year as an Olympic sport.

"I have to tell you. This is Ann's sport. I'm not even sure which day the sport goes on," he said.

"She will get the chance to see it, I will not be watching the event."

Before the Games, the former governor will hit the campaign trail holding high-profile talks with Britain's leaders and meetings with US Olympic athletes.

He is due to hold talks with Cameron, Deputy Prime Minister Nick Clegg, foreign minister William Hague and finance minister George Osborne on Thursday.

Opposition Labour leader Ed Miliband, former prime minister Tony Blair and Irish prime minister Enda Kenny are are also due to meet with Romney before he jets off to Israel after the ceremony.

It was also reported that he will host fundraising dinners for his supporters in London.