North Korea is willing to talk to the United States about denuclearization, a senior U.S. official said Sunday.

These are the first tangible signs that North Korean leader Kim Jong Un is still willing to meet with President Donald Trump since the North first proposed the summit last month.

Trump has said he wants to meet with Kim before the end of May. Details on the talks are still unclear, including the exact agenda and place.

But U.S. officials have said there have been secret contacts between Washington and Pyongyang.

Trump has consistently called for the denuclearization of the Korean peninsula.

In the past, North Korea pledged to freeze its nuclear program in exchange for food aid and easing economic sanctions. Those promises were always broken.

Harry Kazianis, director of defense studies at The Center for the National Interest in Washington, says North Korea is going to make some kind of demand just to have the talks take place, and that its demands for agreeing to abandon its nuclear weapons "are going to be astronomically high."

"They could ask for hundreds of billions of dollars in economic aid," Kazianis told VOA. "They could ask for the removal of U.S. troops from the Korean peninsula. They could even ask for say South Korea to get rid of all of its nuclear technology and nuclear reactors."