Former president Jimmy Carter has appealed for a new drive to engage North Korea, but US officials kept their distance and insisted the regime prove it is ready to give up nuclear weapons.

As a US envoy wrapped up a tour of North Korea's neighbors, Carter made his first public remarks on his trip to the reclusive state last month, saying that leaders told him they wanted better relations with the world.

"A settlement on the Korean Peninsula is crucial to peace and stability in Asia, and it is long overdue," Carter wrote in Thursday's New York Times.

"These positive messages from North Korea should be pursued aggressively and without delay, with each step in the process carefully and thoroughly confirmed," Carter said.

The former president met senior North Korean leaders -- although not supremo Kim Jong-Il, who was visiting main ally China -- on a mission to free an American teacher imprisoned in the communist state.

Carter, who brokered a deal during a nuclear crisis on the divided peninsula in 1994, said that leaders in Pyongyang voiced concern to him over recent pressure by South Korea and the United States.

"Still, they said, they were ready to demonstrate their desire for peace and denuclearization," Carter said.

The remarks come amid new mystery about North Korea after the ruling party apparently delayed its biggest meeting in three decades, citing damage from storms.

Many North Korea watchers expected the meeting to anoint Kim's youngest son, Kim Jong-Un, as his successor. Kim Jong-Il is in uncertain health after suffering an apparent stroke in 2008.

While making no predictions on succession, Carter said he spoke with Chinese Premier Wen Jiabao, who quoted Kim Jong-Il as saying that the promotion of Kim Jong-Un was "a false rumor from the West."

Carter, a Nobel Peace Prize winner, has long been unpopular among US hawks who favor a more muscular foreign policy.

Senator Joseph Lieberman of Connecticut, an independent who was the 2000 vice presidential nominee of Carter's Democratic Party, denounced Carter's views as "awful."

He noted that Carter made no mention of the March sinking of South Korea's Cheonan vessel that left 46 sailors said. South Korea and the United States say the North torpedoed the vessel; Pyongyang denies the charges.

"He fails to mention the Cheonan incident and that certainly puts in doubt his conclusion that the leadership of North Korea that he spoke to is anxious to re-engage again," Lieberman said.

The administration of President Barack Obama, also a Democrat, took its distance from Carter's views.

Kurt Campbell, the assistant secretary of state for East Asia, said that North Korea's appeals for talks were "well known to us."

"Frankly, I too was surprised by the omission of the Cheonan in President Carter's op-ed today," Campbell said, while voicing gratitude to Carter for securing the freedom of English-language teacher Aijalon Mahli Gomes.

State Department spokesman Philip Crowley said US officials briefed the former president on the Cheonan sinking before he went to North Korea.

"For someone of President Carter's stature as a former president, as a Nobel laureate, of course his views carry weight," Crowley said. "But by the same token, the sinking of the Cheonan is a fact. It was a provocative act."

The Obama administration has supported dialogue with US adversaries around the world but has hesitated on North Korea, instead stepping up sanctions after its missile and nuclear tests last year.

Stephen Bosworth, the US pointman on North Korea, wrapped up a week of talks in China, Japan and South Korea by saying that Washington would continue consultations but that "the burden is quite clearly" on Pyongyang.

"I think we need to see some signal from the North Koreans that they are truly serious about fulfilling the commitments they have made in terms of steps toward denuclearization," Campbell said in Washington.

"And I think some of the actions we have seen call into question whether they are prepared to take those steps,' he said.

North Korea agreed in 2005 under the six-nation talks -- which include China, Japan, the two Koreas, Russia and the United States -- to give up its nuclear weapons in return for badly needed aid and security guarantees.