South Korean Foreign Minister Kang Kyung-wha says Seoul is closely communicating with Washington about sending South Korean experts to inspect North Korea's demolished Punggye-ri nuclear testing site.

She told lawmakers Wednesday that a prospective declaration to end the Korean War would become "invalid" if Pyongyang were to carry out a provocation after if were issued.

She said UN Security Council resolutions will remain in place until Pyongyang's full denuclearization is confirmed.

She also said the two Koreas' joint project to connect their railways are currently focused on joint research, and is expected to expand after changes are made to the sanctions.