North Korea is expected to repatriate the remains of an unspecified number of U.S. soldiers who died in the 1950-53 Korean War as early as Friday, diplomatic sources said Thursday.

The remains are expected to be flown to a U.S. military base in South Korea from an airport in Wonsan, northeastern North Korea. Friday falls on the 65th anniversary of the signing of the 1953 armistice agreement that halted hostilities in the Korean War.

The repatriation of the remains was promised by North Korea to the United States at a historic summit between the two countries last month in Singapore.

The move comes as North Korea has suggested it wants to see a declaration made public on ending the Korean War before taking concrete steps toward the denuclearization of the Korean Peninsula.

Yonhap News Agency reported Thursday that North Korea seems to have completed preparations for the remains' return and is expected to hand them over on Friday, citing a diplomatic source in Seoul.

The South Korean Unification Ministry said the same day that the North has received wooden boxes for storing remains that the United States had sent to the border village of Panmunjeom.

The JoongAng Ilbo, one of the South's major newspapers, said Thursday that U.S. transport aircraft will be used in the repatriation.

Amid speculation that the transfer may involve around 50 sets of remains, the newspaper quoted a U.S. government source as saying that the number remains unclear until the remains are actually received.