The remains were scheduled to arrive tomorrow in Hawai'i, where they will be taken to the Joint POW/MIA Accounting Command to undergo forensic identification.

New Mexico Gov. Bill Richardson and Anthony Principi, former U.S. veterans affairs secretary, were greeted at the frontier between North and South by U.S. Ambassador to South Korea Alexander Vershbow and U.S. military officials.

Richardson spent four days in North Korea, also joined by the top White House adviser on Korea, Victor Cha.

"Hopefully, we've done our bit to relieve the tension between our two countries," Richardson said after crossing the border, referring to the U.S. and the North.

While in the North on a mission to recover the remains of the U.S. soldiers, the delegation met with officials to press Pyongyang to meet a Saturday deadline to shut down its sole operating nuclear reactor under a February agreement with the U.S. and other regional powers.

It's unclear if the deadline will be met due to a separate dispute over frozen North Korean funds that Pyongyang has insisted be resolved before it moves to disarm.

Authorities in the Chinese territory of Macau, where North Korea had its accounts, said today that the money is now free for withdrawal. North Korea has yet to say whether it is satisfied with the resolution of the issue.

Today, the Americans drove two hours from the North Korean capital Pyongyang along virtually traffic-free roads, seeing farmers working fields with their hands and people walking along the highway. The remains of the soldiers were transported separately in small, black cases.

Before crossing into the South, the delegation toured the buildings where the armistice that ended the Korean War was negotiated and signed, with a guide showing them where each party sat.

They then walked across the North-South frontier at the truce village of Panmunjom, where the two Koreas stand face-to-face across the border that has divided the peninsula since the 1953 cease-fire.

Principi said the mission to deliver the remains was one of the most emotional moments of his life.

"To participate in such a noble mission to bring home the remains of men who 50 years ago were in harm's way, and now they're home, it was really quite moving," he said.

More than 33,000 U.S. troops died in the Korean War, which began in June 1950 when North Korea invaded South Korea. Some 8,100 U.S. servicemen still are listed as missing.

In 2005, the U.S. government halted a separate cooperative program that permitted U.S. military teams to excavate remains from North Korean battlefields, saying the North had created an unsafe environment. The program had recovered remains believed to be from 220 soldiers since 1996.

North Korea has no plans to resume the joint recovery operations, Richardson's Asian affairs adviser, K.A. "Tony" Namkung said, citing comments by North Korean Gen. Ri Chan Bok. Namkung said Ri had offered the six sets of remains as a gesture in return for Richardson's reconciliation efforts.

Once in South Korea, the U.S. delegation flew on a Black Hawk helicopter to Yongsan Garrison, the main U.S. military headquarters on the peninsula in central Seoul. From above, they saw the stark difference between the communist North and capitalist South Korea, where throngs of cars stream down modern highways and high-rise buildings stretch into the distance.