WASHINGTON (AFP) - Prince Harry, in the dress uniform of his British army regiment, paid tribute Friday to United States (US) soldiers killed in Iraq and Afghanistan on day two of a US tour dedicated in good part to war veterans.

With white-gloved hands behind his back, he strolled alone through rows of white headstones in a section of the sun-kissed Arlington National Cemetery reserved for those who died in America's most recent wars.

He wore the dark blue uniform of the Blues and Royals cavalry regiment, which he joined in 2006, together with a powder blue beret representing his role as an Apache attack helicopter pilot in the British army's air wing.

On a floral arrangement, the 28-year-old captain - who has twice deployed in Afghanistan - left a signed handwritten note: "To my comrades-in-arms of the United States of America, who have paid the ultimate sacrifice in the cause of freedom," it said.

Harry also laid a wreath at the Tomb of the Unknown Soldier at Arlington, watched by a youthful crowd of T-shirted tourists kept at a distance behind a metal barricade, and paused at the grave of president John F. Kennedy, assassinated 50 years ago this November.

Later in the day, he crossed town to the Walter Reed National Military Medical Center to mingle with US soldiers undergoing physical therapy and get a private briefing on the latest breakthroughs in prosthetics.

On the weekend, Harry will be in Colorado for the Warrior Games, where 200-plus wounded servicemen and women will compete in such sports as archery, cycling, swimming, track and field, and wheelchair basketball.

Harry, who last visited Washington a year ago, is on his best behaviour after cellphone naked photos of him partying in a Las Vegas hotel suite spilled onto the Internet last August.

Like his father Prince Charles and older brother Prince William, he is assuming a bigger share of royal duties on behalf of his grandmother Queen Elizabeth II, who turned 87 last month.

Harry began his week-long US tour on Thursday with a visit to a Capitol Hill photo exhibit on land mine clearance efforts around the world - ignoring the dozens of excited young Senate staffers and interns who turned out to catch a glimpse of Britain's most eligible bachelor.

He also popped into the White House for afternoon tea with First Lady Michelle Obama and US military veterans, in an event that did not feature on his official schedule.

Harry is the 25th anniversary fund-raising patron of the Halo Trust, the world's biggest mine-clearing organisation and a favorite charity of his mother Princess Diana prior to her death in a 1997 car crash in Paris.

Its director Guy Willoughby told AFP that if funding - including millions of dollars from the US - can be sustained, all mine fields in post-conflict areas of Africa and Asia could be cleared in five to 10 years.

Next Tuesday, Harry will be in New Jersey to see first-hand the damage inflicted on the Mid-Atlantic state by superstorm Sandy in October.

He'll also attend a charity polo match in Connecticut before returning home.