A senior South Korean government official said Friday that North Korean leader Kim Jong-un had a special message delivered to U.S. President Donald Trump apart from his proposal for summit talks with the U.S.

Speaking to correspondents in Washington, the official did not say what that message was, but did indicate it is part of trust-building efforts to realize the summit.

Asked if the special message concerned denuclearization, the official only said "it is very comprehensive."

The official added that when South Korea's national security adviser and envoy to North Korea Chung Eui-yong delivered that message verbally to President Trump at the White House on Thursday, Trump showed a "very positive" response.

The official said he expected working-level contacts to begin between Washington and Pyongyang before the summit talks and also projected moves such as the dispatch of envoys and meetings of high-level officials.