The United States on Tuesday marked the 69th anniversary of the outbreak of the Korean War, calling it a history that should be taught, not forgotten.

The three-year conflict, which ended in an armistice and not a peace treaty in 1953, has sometimes been referred to as "The Forgotten War" in the English-speaking world because it received less public attention than World War II, which preceded it, or the Vietnam War, which succeeded it.

"The Korean War anniversary is a reminder of allied troops' selfless bravery and US and ROK resolve to defend liberty against aggression in the past and future," US State Department spokeswoman Morgan Ortagus wrote on her official Twitter account.

ROK stands for South Korea's official name, the Republic of Korea.

"This history should be taught in our #IndoPacific region and around the world -- not forgotten or distorted," she said.

The US fought alongside South Korea under the United Nations flag against an invasion by North Korea, which was backed by China and the Soviet Union. More than 36,000 U.S. troops were killed in the conflict.

At the Korean War Veterans Memorial in Washington, some 200 veterans and officials gathered to commemorate the war and pay tribute to the fallen.

South Korean Ambassador to the US Cho Yoon-je expressed the nation's gratitude to the 22 states that sent troops and other support under the UN flag.

"Your sacrifices allowed my country to achieve our unprecedented economic growth and our hard won democratic freedom," Cho said. "But we still have one mission to complete: the establishment of permanent peace on the Korean Peninsula.

"I know that some are concerned about our chances for success. But the legacy of the Korean War veterans suggests to me that, when we base our efforts on the steadfast ROK-US alliance and our friends around the world, we can succeed, no matter how difficult the task may be," he said.

Paul Cunningham, president of the Korean War Veterans Association, noted that at the annual event exactly a year ago he spoke of the hope of peace brought by the June 12, 2018, summit between US President Donald Trump and North Korean leader Kim Jong-un.

"Sadly, except for the return of 55 coffins with the remains of some of the fallen, little else has been accomplished," Cunningham said, referring to the remains of American soldiers that were returned by North Korea after the summit.

The 89-year-old veteran served as a radar repairman with the Air Force during the war.

"I would suggest that we redouble our resolve by seeking to have our leaders renew efforts to achieve and sustain peace, a nuclear free and unified Korea and the return of the remains of our fallen comrades," he said. (Yonhap)