A key official of the National Security Council (NSC) said Monday the government will announce next month the cost for relocating all U.S. troops in Seoul to outside the capital city.

The official said on condition of anonymity that about 90 percent of the details had been agreed at working-level negotiations between South Korea and the U.S., adding that the council will announce all points of the cost in the coming month.

He explained that Seoul would not pay the entire cost in cash but also partly in services.

The two allies agreed in Honolulu over the weekend to relocate the U.S. Yongsan Garrison, which houses 7,000 U.S. military personnel, out of central Seoul over the next three years.

South Korea is expected to shoulder most of the relocation costs, estimated at US$3-4 billion.