Republican presidential candidate Mitt Romney has caused a stir on his overseas tour by questioning whether Britain is prepared to pull off the Olympic Games without problems.

"It's hard to know just how well it will turn out," Romney told NBC News, and he called the late-developing concerns over security staffing "disconcerting."

Romney, a former businessman and one-term governor who managed the Salt Lake City Olympics in 2002, is largely untested on the world's political stage, and he hopes to assert himself in a tight and highly expensive presidential race with foreign visits that also include Israel and Poland.

He ended up putting Prime Minister David Cameron at least briefly on the defensive. In response to Romney's remarks, the prime minister said, "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."

He apparently was referring to Utah, the site of the Games Romney managed. The lively British media pounced. "PM delivers Olympic putdown to Romney," the Times in London trumpeted.

Informal diplomacy for presidential candidate

Meeting with British officials is typically one of the first priorities of any new U.S. president, and establishing those relationships beforehand can help any transition. President Barack Obama met with British leaders when he took a trip abroad while campaigning for president in 2008.

During the public portion of his meeting with Cameron, Romney tried to smooth over his earlier comments. "It is impossible for absolutely no mistakes to occur," he said. "Of course there will be errors from time to time, but those are all overshadowed by the extraordinary demonstrations of courage, character and determination by the athletes."

After the meeting, Romney told reporters that he and Cameron spoke "at length" about Syria as well as Libya, Pakistan and other countries. He did not give details, saying discussion of foreign policy should be made by the president and the administration overseas and not by those seeking office. He did thank British soldiers for fighting alongside U.S. troops in Afghanistan.

It wasn't Romney's first meeting with Cameron. The two also talked during a Romney visit to London in 2011. This year, Cameron travelled to the U.S., where he met Obama and attended a state dinner in Washington but did not meet with Romney.

Romney also will spend part of his time in London raising money and highlighting his Olympics experience with an appearance Friday at the opening ceremony of the London Games.

On Thursday, Romney also met with former Prime Minister Tony Blair; Ed Miliband, the current leader of the Labour Party — the opposition to Cameron's Conservative Party; and Foreign Secretary William Hague. The candidate also met with Nick Clegg, the deputy prime minister, and Chancellor of the Exchequer George Osborne, Britain's top financial official.

White House unimpressed

The meetings come a day after the Daily Telegraph published a story quoting an unidentified Romney campaign adviser saying the Republican believes the U.S. relationship with Britain is special because of shared "Anglo-Saxon heritage" that the adviser said the White House doesn't appreciate.

Romney, however, quickly distanced himself from any such view.

"I don't agree with whoever that adviser might be," Romney told NBC News, "but do agree that we have a very common bond between ourselves and Great Britain."

Nonetheless, Vice-President Joe Biden and top Obama aides criticized Romney. "The comments reported this morning are a disturbing start to a trip designed to demonstrate Gov. Romney's readiness to represent the United States on the world's stage," Biden said.

Accompanying Romney to some of his meetings Thursday were former Missouri Senator Jim Talent, an adviser, and Kerry Healey, who served as lieutenant-governor when Romney was governor of Massachusetts. Three of Romney's sons — Tagg, Josh and Craig — also have joined him in London.