US Secretary of State Mike Pompeo on Sunday held out a brighter future for North Korea, urging leader Kim Jong-un to follow the path to prosperity taken by Vietnam.

Pompeo was speaking at a business event in Hanoi, Vietnam, after completing a two-day trip to Pyongyang where he met with North Korean officials to discuss the details of a summit agreement between US President Donald Trump and Kim.

"In light of the once-unimaginable prosperity and partnership we have with Vietnam today, I have a message for Chairman Kim Jong-un: President Trump believes your country can replicate this path," Pompeo said. "It's yours if you'll seize the moment. The miracle could be yours; it can be your miracle in North Korea as well."

The Trump administration has repeatedly offered economic incentives for North Korea to dismantle its nuclear weapons and ballistic missile programs. At last month's summit in Singapore, Kim committed to work towards the "complete" denuclearization of the Korean Peninsula in exchange for security guarantees from the United States.

Pompeo was in Pyongyang last week to flesh out that deal. He later said there was progress in talks, including on setting a timeline for denuclearization, but also acknowledged much work remained to be done.

Meanwhile, North Korea lashed out at the US shortly after Pompeo left, saying the top US diplomat presented a "unilateral and gangster-like" demand for "complete, verifiable and irreversible" denuclearization, a longstanding US goal.

"The United States has been clear about what we seek from North Korea to set in motion this great chain of events," Pompeo said in Hanoi. "The choice now lies with North Korea and its people. If they're able to do this, they will be remembered and Chairman Kim will be remembered as a hero of the Korean people."

Pompeo recounted the path Vietnam took from a series of wars in the 20th century to building the fastest-growing economy in Southeast Asia.

"One key to Vietnam's enormous rise over the past few decades was a new engagement with the United States of America. This began when the US -- the United States and Vietnam began working together to repatriate the remains of American service members lost in Vietnam," he said. "This small but incredibly meaningful first step eventually helped lead to better ties and formal reestablishment of our relationship in 1995. This is the same issue that the United States faces today with Chairman Kim, where new ties with America combined with the industriousness of the Vietnamese people and sound leadership has made Vietnam an incredible success story today."

There was speculation that during his trip to Pyongyang, Pompeo would bring back the remains of some American soldiers killed in the 1950-53 Korean War. Repatriating the remains was part of the summit agreement between Trump and Kim.

Despite the expectations, the remains were not returned and Pompeo was not granted a meeting with Kim.

On his two previous trips to Pyongyang, the secretary of state met with Kim to lay the groundwork for the summit. (Yonhap)