LONDON—For the second day in a row, Mitt Romney's visit to London was marred by controversy, as the British media seized on comments the GOP candidate made suggesting he found London's preparations for the 2012 Summer Olympics "disconcerting."

In an interview with NBC News on Wednesday, Romney, who has campaigned on his experience running the 2002 Winter Olympics in Salt Lake City, was asked if he thought London was "ready" for the games.

"You know, it's hard to know just how well it will turn out," Romney told NBC. "There are a few things that were disconcerting. 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."

Romney's comments were immediately big news in London, splashed across the websites of major newspapers. In a press conference Thursday just hours before he was set to meet with Romney, Prime Minister David Cameron issued a snippy rejection of Romney's comments.

"We are holding an Olympic Games in one of the busiest, most active, bustling cities anywhere in the world. Of course it's easier if you hold an Olympic Games in the middle of nowhere," Cameron said, a comment that was widely interpreted as a reference to Salt Lake City, where Romney headed up the organizing committee.

Cameron told reporters he looked forward to addressing the subject with Romney during their meeting at No. 10 Downing Street—and presumably he did.

Emerging after his sit-down with Cameron to speak to more than 100 reporters waiting outside the prime minister's office, Romney immediately heaped effusive praise on the London games. He spoke of how the games would energize "millions" of people in the city and how nice it was to look out the back windows of No. 10 Downing Street to see an Olympic venue—right in the "heart of London," he noted.

"What I see shows imagination and forethought and a lot of organization, and I expect the games to be highly successful," Romney said.

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Asked about his comments to NBC, Romney suggested they had not been meant as an insult and repeatedly praised London organizers. He said that no Olympics has ever been pulled off without mistakes—not even the Olympics he ran in Salt Lake City.

"My experience with Olympic organizing is that there's always a few very small things that end up going not quite right the first day or so," Romney said. But the issues always get "ironed out," he added.

The flap over Romney's Olympics comments comes just a day after his campaign went on the defense after the Daily Telegraph quoted an unnamed Romney adviser suggesting President Barack Obama did not fully appreciate the "Anglo-Saxon heritage" between the United States and Great Britain. The Romney campaign immediately insisted the comment didn't come from anyone affiliated with the campaign—a position later echoed by the candidate himself, who told NBC he believes Obama does understand the special relationship between the U.S. and Britain.

Both controversies threatened to overshadow a trip that Romney aides hoped would help the GOP candidate boost his credibility on foreign policy issues, an area where some believe his resume is lacking. The stir over Romney's Olympics comments could also undermine another goal of the trip: to call attention to Romney's successful stewardship of the Salt Lake City games.

Speaking to reporters outside No. 10 Downing Street, Romney did damage control, going on at length about the enthusiasm around the games and how well the games appeared to be organized.

"This is an indication of a community that will share in the Olympic experience, be unified and uplifted by it, and I am delighted," Romney said.