Seoul, South Korea ? The first high-level U.S. envoy to visit North Korea in two years said Saturday that he expressed to the North’s officials “serious concerns” about the communist country’s weapons, human rights record and humanitarian crisis.

Assistant Secretary of State James Kelly said no date had been set for another round of talks with a nation that President Bush has labeled part of an “axis of evil.”

“I felt that our exchanges in Pyongyang were frank, as befits the seriousness of our differences, and they were useful, too,” Kelly said in a statement at the South Korean Foreign Ministry after flying on a U.S. military plane from North Korea.

There was no suggestion that deals were imminent, and the talks between two Korean War foes that have traded harsh criticism since Bush took office appeared to be the beginning of a long, difficult process.

But they were a long-awaited step forward for North Korea and the United States, which says the North is the world’s foremost exporter of missile technology, and a threat to regional and even global stability.

The North, in turn, has accused Washington of trying to isolate and undermine its government, and has long demanded the withdrawal of U.S. troops from South Korea.

The negotiations, which began Thursday, coincided with North Korean overtures to South Korea and Japan, both American allies, as well as a partial loosening of economic controls in the totalitarian state.

There is a widespread belief in Seoul and Washington that North Korea is reaching out because its leader, Kim Jong Il, realizes he can’t salvage his economy without the help of his traditional adversaries.