Stephen Bosworth sounded a hopeful note, calling his three-day visit to North Korea "very useful" and citing a "common understanding" with his North Korean counterparts on the importance of the denuclearization process.
The six-nation talks have been stalled for a year, during which time the reclusive communist regime has conducted a nuclear test and ballistic missile test-launches, and claimed it restarted its atomic program.
"It is certainly our hope, based on these discussions in Pyongyang, that the six-party talks can resume expeditiously and that we can get back to the important work of denuclearization," Bosworth told a news conference in Seoul after returning from Pyongyang.
The veteran diplomat's talks in North Korea were the first high-level contact between Washington and Pyongyang since Obama took office in January pledging to reach out to former adversaries.
Six nations - the two Koreas, the U.S., Russia, Japan and China - had been negotiating since 2003 on a step-by-step process to dismantle North Korea's nuclear program.
North Korea walked away from those talks earlier this year in anger over the international criticism of its ambitions to develop rocket technology, widely seen as a test of its long-range missile delivery system.
After months of rising tensions and inflammatory rhetoric, North Korea began reaching out to the U.S. and other participants in the six-party talks in recent months.
North Korea has long sought diplomatic relations with the U.S., which fought for the South Koreans during the three-year Korean War of the 1950s. Washington still has 28,500 troops stationed in South Korea, which technically remains at war with the North because they signed a truce, not a peace treaty, in 1953.
Pyongyang routinely accuses Washington of having designs to attack North Korea, and cites the U.S. military presence on the peninsula as a chief reason behind its push to build up its atomic arsenal. The U.S. denies seeking to invade the North.
In August, former U.S. President Bill Clinton traveled to the reclusive nation on a private humanitarian mission to negotiate the release of two detained American journalists. He sat for three hours with Kim Jong Il - the North Korean leader's first public appearance with a high-profile figure in a year - in a meeting that appeared to break the ice between the two nations.
Bosworth said Thursday that he did not request a meeting or meet with Kim Jong Il. North Korea's state media said Kim was traveling outside Pyongyang during the three days of Bosworth's visit.
He said he met with Kang Sok Ju, the first vice foreign minister considered Kim's chief foreign policy strategist, and top nuclear envoy Kim Kye Gwan.
Bosworth characterized the "candid" discussions as "exploratory talks" rather than negotiations, and said he did not succeed in gaining Pyongyang's firm commitment on returning to the disarmament talks.
It "remains to be seen when and how the DPRK will return to the six-party talks," he said, referring to North Korea by its official name, the Democratic People's Republic of Korea. "This is something that will require further consultations among all six of us."
But he added, "there is a common understanding" on the need to resume the disarmament process.
Bosworth said he conveyed Obama's message stressing the importance of the need for a "complete denuclearization of the Korean peninsula."
"As President Obama has made clear, the United States is prepared to work with our allies and partners in the region to offer North Korea a different future," Bosworth said, adding that discussion of a peace treaty could be part of future six-party negotiations.
"The path for North Korea to realize this future is to choose the door of dialogue in the six-party talks and to take irreversible steps to achieve the denuclearization of the Korean peninsula," he said.
South Korea's unification minister, Hyun In-taek, called the flurry of diplomacy a "turning point."
"The situation on the Korean peninsula has become increasingly flexible. The peninsula and inter-Korean relations are now at an important turning point," he said Thursday, according to the Yonhap News Agency.
Bosworth was accompanied by chief U.S. nuclear negotiator Sung Kim, as well as atomic and Asia specialists from the Defense Department and the White House. The delegation heads Friday to China, Japan and Russia to brief the six-party partners on the Pyongyang trip.