North Korea says it will respond "very strongly" to a conference in Washington on Tuesday about its widespread human rights abuses and says the United States ignored Pyongyang's offer to attend and defend itself. Puzzled conference organizers said the event was open to the public.

North Korea's U.N. Ambassador Jang Il Hun told reporters Monday his country has asked the U.S. government to "immediately scrap the so-called conference" hosted by the nonprofit Center for Strategic & International Studies. Speakers include Robert King, the U.S. special envoy for North Korean human rights issues.

Victor Cha, Korea chair at CSIS, said he was not sure what Jang was referring to. "We issued no specific invitations to anyone," he said.

Nuclear-armed North Korea has been on the defensive ever since a groundbreaking U.N. commission of inquiry detailed vast rights abuses there. International pressure behind last year's report led the U.N. Security Council to place the issue on its agenda of matters of international peace and security.

Jang said he sent a formal request to his counterpart in the State Department and that the counterpart responded that the conference was not a government one. "That means our request was denied," Jang said.

North Korea and the United States do not have formal diplomatic relations, but Jang is tasked with communicating through the so-called "New York channel" that the country's U.N. mission uses to reach out to U.S. officials. Jang said his communication to the U.S. was only about the conference.

The U.S. restricts North Korean diplomats to traveling within a 25-mile (40-kilometer) radius of midtown Manhattan, and they must request permission to go farther.

The State Department said the conference was a privately organized event.

North Korea has repeatedly said the U.S. uses the human rights issue as a pretext to overthrow it, and it has started demanding that the U.S. should instead look into the CIA's "torture crimes."

The U.N. General Assembly in December approved a resolution that urged the council to refer North Korea's human rights situation to the International Criminal Court, and the head of the commission of inquiry has written to North Korean leader Kim Jong Un warning that he could be held accountable for crimes against humanity.

"We are not guilty of any crime," Jang said Monday, smiling.

But alarmed by anything targeting their young leader, North Korean diplomats briefly proposed last year that the U.N. high commissioner for human rights could visit their country if the U.N. resolution would drop the language about Kim and the ICC.

Jang on Monday told reporters that the opportunity had passed. "Once it's gone, we have to start all over again," he said.

Jang also has said his foreign minister was not allowed to attend a meeting with Secretary of State John Kerry and other diplomats about North Korea's human rights during the U.N. General Assembly of world leaders last fall.

Another organizer of Tuesday's conference, Greg Scarlatoiu with the Washington-based Committee for Human Rights in North Korea, said he had not heard from North Korea about it. "I find it encouraging that North Korea is paying attention to a conference commemorating one year since the release of the report, since they've been unwilling to accept the commission of inquiry," he said.