WASHINGTON -- The United States remains committed to the South Korea-US alliance, 71 years after the start of the Korean War, a Pentagon spokesman said Thursday, calling the alliance the "linchpin of peace" for the region and the world.

Department of Defense spokesman John Kirby made the remarks as the allies mark the 71st anniversary of the start of the 1950-53 Korean War on Friday.

"Tomorrow marks 71 years since the start of the Korean War. For the past 71 years our commitment to the alliance has been ironclad, built on the shared sacrifice of Americans and South Koreans," he said at a press briefing.

"The US-ROK alliance is the linchpin of peace, security and prosperity for Northeast Asia and a free and open Indo-Pacific, as well as across the world," he added, referring to South Korea by its official name, the Republic of Korea.

South Korea and the United States formally established their alliance in 1953 when they signed a mutual defense treaty.

The US is one of 16 UN member countries that sent troops to South Korea to help defend it in the war that left more than 36,000 American soldiers dead, along with nearly 168,000 South Korean troops.

South Korea and the North continue to remain at war technically as the 1950-53 war ended only with an armistice, not a peace treaty.

Kirby noted the Pentagon is not planning any formal event to mark the war's beginning, but said it was an important milestone, and "a reminder of how long ago that was -- but how still so significant and important security on the Korean Peninsula remains to the United States."

The US currently maintains some 28,500 troops in South Korea as a legacy of the Korean War.

Earlier reports said some 3,700 US troops recently arrived in South Korea to relieve others.

The Pentagon spokesman said the troops are from the 3rd Armored Brigade Combat Team of the 1st Armored Division, based at Fort Bliss, Texas. They will be part of what he called a normal and "long scheduled rotation."

"The 3rd Armored Brigade Combat Team will replace the 1st Brigade Combat Team, 3rd Infantry Division, as part of a regular rotation of forces to support the United States' commitment to the Republic of Korea. So this is a normal rotational deployment," he said. (Yonhap)