WASHINGTON (AFP) - Britain's Prince Harry broke hearts in Washington's corridors of power on Thursday, showing more interest in landmines than in the excited female staffers and interns who turned out to greet him at the start of a week-long visit to the United States.

Squeals ricocheted down the halls of the Russell Senate office building on Capitol Hill as the 28-year-old eligible bachelor inspected a photo exhibit set up by the Halo Trust, a charity favored by his late mother Princess Diana.

Prince Harry, a British army officer in Afghanistan, ignored the giddy posse of twentysomethings as he chatted with Senator John McCain, 76, a Vietnam war veteran whose wife Cindy McCain is a Halo Trust board member.

There were no public remarks, but Prince Harry was overheard inquiring about the price of mine detectors when he cast an eye over mannequins in cobalt blue outfits combing the polished marble floor for imaginary unexploded ordnance.

Prince Harry is the honorary fund-raising patron of the Halo Trust, the world's biggest demining organisation, which since its founding 25 years ago has unearthed more than 1.4 million landmines in 9,800 minefields around the world.

"He's very much tuned in to the landmine issue," said Halo Trust chief executive Guy Willoughby, who also conversed with Prince Harry at the exhibit aptly installed outside the Senate armed services committee hearing room.

Princess Diana famously toured minefields cleared by Halo teams in Angola shortly before her death in a Paris car crash in August 1997, a year after her stormy divorce from Prince Charles, heir to the British throne.

The United States is the only Nato member state not to sign the 1997 Ottawa treaty banning landmines, but since the late 1990s it has contributed US$150 million (S$184 million) to support the Halo Trust's work.

"The commitment of the American government to fund humanitarian mine clearance far, far, far outweighs the political niceties about whether they have or have not signed the Ottawa treaty," Mr Willoughby told AFP.

If funding levels are sustained, he said, it would be possible to clear virtually every minefield in every erstwhile combat zone in Africa and Asia in the next five to 10 years.

A State Department official said Washington is "the world's single largest financial supporter of demining and conventional weapons destruction," even as it pursues "an ongoing policy review" on whether to adopt the Ottawa treaty.

"Since 1993, we have delivered over US$2 billion in more than 90 countries for mine clearance, survivor assistance, mine risk education, and the research and development of new demining technologies," the official told AFP.

Prince Harry paid a surprise visit on Thursday to the White House where First Lady Michelle Obama offered him afternoon tea in the company of American military veterans.

"He has a very busy schedule, but when he heard about this tea and all of you ... he wanted to be here to personally thank you for your service," she said as Prince Harry kept a polite silence.

Prince Harry is on his best behaviour after photos of the party-loving prince in a Las Vegas hotel suite - totally naked, with hands cupped over his crown jewels - spilled onto the Internet last August.

His official schedule in Washington also included a dinner Thursday at the British ambassador's residence - with roasted veal and a salad of scallops on the menu - and a solemn wreath-laying Friday at Arlington National Cemetery.

From the US capital, he'll proceed to Colorado to open the Warrior Games for wounded military personnel, then go on to New Jersey to see first-hand the damage inflicted on the Atlantic coast state by superstorm Sandy last October.