Bush slipped out of the White House just after 7:00 am (1100 GMT) to visit the Korean War Veterans Memorial, on the opposite side of Washington's central mall.

Gravely and slowly, he toured the monument, a set of 19 steel statues of US troops marching in grim formation towards an unknown destination.

"There is a very profound statement here at this moving memorial, it says, 'Freedom is not free,'" Bush told reporters.

"Those who served in Korea also remind us of the challenges we face today, and it gives us a chance to reflect on the sacrifices that are being made on behalf of freedom today," said Bush who directs US wars in Afghanistan, Iraq and against terrorism.

"Our nation will be eternally grateful for the men and women who serve today, as we are for those who have served in the past," said Bush.

The armistice which ended the three-year war between US, South Korean and allied forces and a North Korean army backed by China on July 27, 1953, never matured to a full peace treaty.

The Cold War between North Korea and the United States has several times since approached boiling point.

Washington has been locked in an intense nuclear crisis with Pyongyang since last October, and is calling for the Stalinist state to take part in mulilateral talks to search for a solution.

In a reminder of current tensions Friday, Washington imposed new sanctions on Pyongyang after finding that an already punished firm in the country had continued to violate US law with the sales of missile parts and technology.

The State Department said that Changgwang Sinyong Corporation, would be sanctioned for sending 15 Scud missiles to Yemen.

Spanish navy vessels intercepted the shipment, contained on an unflagged merchant vessel off the Yemeni coast last year, but US officials concluded they had no legal grounds to prevent their delivery.

The firm had been in violation of US arms export control laws on at least five previous occasions.

Despite Bush's trip to the memorial, and previous efforts by his predecessor Bill Clinton to honor Korean War veterans, many feel their sacrifice has been ignored.

The conflict, in which 37,000 US and allied troops perished, has become known as the "forgotten war."

The memorial was only opened in 1995, more than 40 years after the end of the war, after years of campaigning by veterans groups.

Neither tickertape nor parades greeted US soldiers who limped home from the Korean War, and 50 years on, many veterans still ask why their sacrifice seems forgotten by history.

Commemorations marking half a century since hostilities that ended this weekend are tinged with extra sadness, as it will be perhaps the final time that many veterans, now into their 70s and 80s, will gather in large numbers.

"Most of the Korean veterans are very bitter, including myself, because nobody recognises what they did as being very important," said John Connolly, who fought with the 23rd Infantry Regiment, the 2nd Infantry Division.

"People didn't even know the Korean War was going on. They didn't know anything about it," he said, remembering how he returned to the United States after losing an arm in combat.

Sandwiched in time between World War II and the Vietnam War, the Korean War merits only passing mention in US school text books.

Yet it remains one of the most blood-soaked foreign conflicts in US history, with nearly tens of thousands of US and allied troops wiped out along with hundreds of thousands of Chinese, South Korean and North Korean troops and civilians.

WAR.WIRE