Ri Gun, the North Korean Foreign Ministry's chief expert on U.S. affairs, led a delegation that met behind closed doors with former U.S. ambassadors and other North Korea experts in San Diego on Monday and Tuesday and in New York on Friday. No U.S. officials attended Friday's meeting, though a State Department official did go to San Diego.

North Korea carried out nuclear weapons and ballistic missile tests earlier this year, but North Korean leader Kim Jong Il recently said his country could rejoin international disarmament talks, depending on the status of direct talks with the U.S.

North Korea has a longstanding goal of drawing Washington into face-to-face dialogue and cutting other regional powers out of the talks.

The U.S. has said it is willing to hold direct talks with North Korea if it leads to resumption of the six-party talks aimed at halting the country's nuclear weapons programs. The talks would also involve South Korea, China, Russia and Japan.

For the San Diego meetings, the U.S. State Department sent Sung Kim, the U.S. special envoy to the now-suspended six-party talks.

Both sides also met last Saturday when the North Koreans arrived in New York.

However, no State Department representative attended the New York meetings on Friday, and State Department spokesman Robert Wood told reporters in Washington that no further meetings were scheduled between U.S. officials and the North Koreans.

At a news conference Friday following the conclusion of the New York talks, Winston Lord, a former U.S. ambassador to China and assistant Secretary of State for East Asian and Pacific Affairs, said “nobody pulled any punches” in the private talks.

But “the mood was much better than we've seen in months,” Lord said.

Lord said he heard no specific initiatives that would be ice-breakers during the group sessions.

South Korea's Yonhap news agency quoted Ri as saying after the New York meeting that “I had a useful dialogue,” and that he had met with Kim at the request of the U.S. government. He did not comment on other details of his visit.

North Korea has issued an invitation to the U.S. special representative for North Korea policy, Stephen Bosworth, to come to Pyongyang in late November.

But on Thursday, State Department spokesman Ian Kelly told reporters “the U.S. has made no decision for Ambassador Bosworth to accept the invitation of North Korea to have bilateral talks.”

The president of the Korea Society, Evans Revere, confirmed that he had raised the question of a Bosworth visit with Ri Gun privately on Friday.

Revere said that a visit from Bosworth “would be a very appropriate thing” if North Korea took steps to resume dismantling its nuclear weapons program to international inspection and returned to the six-way talks.

Lord was asked whether he had heard anything new from the North Koreans that would lead to a breakthrough, and replied, 'If we did, we wouldn't tell you.'”

“I don't want to suggest any breakthroughs,” Lord added.

The atmosphere sounded similar to the summation of the two-day meeting in San Diego.

Susan Shirk, a University of California-San Diego professor and founder of the Northeast Asia Cooperation Dialogue, said Tuesday after the San Diego talks ended, “I don't see any major breakthroughs.”

The think tank meetings were also co-sponsored by the National Committee on American Foreign Policy and The Korea Society.

North Korea and the United States do not have diplomatic relations, so dialogue between them often takes place unofficially at think tank meetings, and through the North Korean U.N. Mission in New York.