U.S. Secretary of State Mike Pompeo is due to meet with North Korean leader Kim Jong Un on Sunday, the State Department said Tuesday as high-stakes talks over Pyongyang's nuclear weapons program enter a crucial phase.

The top American diplomat's planned visit comes as the two countries seek a breakthrough in the stalled talks and as Pompeo looks to lay the groundwork for a second Trump-Kim summit.

But Tuesday's rare announcement that Pompeo would actually meet with the young North Korean dictator also came just hours after North Korea threw cold water on the idea that a declaration ending the Korean War could be used as a bargaining chip in denuclearization talks — but suggested lifting sanctions might be.