SEOUL/WASHINGTON (Reuters) - South Korean and Chinese officials and sources familiar with U.S. intelligence on Tuesday cast doubt on reports that North Korean leader Kim Jong Un is gravely ill after a cardiovascular procedure, while the White House said it was closely monitoring the matter.

U.S. President Donald Trump, who held unprecedented summits with Kim in 2018 and 2019 in an attempt to persuade him to give up his nuclear weapons, said the reports had not been confirmed and he did not put much credence in them.

“I just hope he’s doing fine,” Trump told a White House news conference. “I’ve had a very good relationship with Kim Jong Un. And I’d like to see him do well. We’ll see how he does. We don’t know if the reports are true.”

Asked whether he would try to reach out to Kim to check on his condition, Trump said: “Well I may, but I just hope he’s doing fine.”

Daily NK, a Seoul-based website, reported late on Monday that Kim, who is believed to be about 36, was recovering after undergoing a cardiovascular procedure on April 12. It cited one unnamed source in North Korea.

Two South Korean government officials rejected a subsequent CNN report citing an unnamed U.S. official saying that the United States was “monitoring intelligence” that Kim was in grave danger after surgery.

South Korea’s presidential Blue House said there were no unusual signs from North Korea.

Earlier, Trump’s national security adviser, Robert O’Brien, told Fox News the White House was monitoring the reports “very closely.”

Bloomberg News quoted an unnamed U.S. official as saying the White House was told that Kim had taken a turn for the worse after the surgery.

However, authoritative U.S. sources familiar with U.S. intelligence questioned the report that Kim was in grave danger.

A Korea specialist working for the U.S. government said, “Any credible direct reporting having to do with Kim would be highly compartmented intelligence and unlikely to leak to the media.”

Kim is a third-generation hereditary leader who rules North Korea with an iron fist, coming to power after his father Kim Jong Il died in 2011 from a heart attack.

Reporting from inside North Korea is notoriously difficult, especially on matters concerning its leadership, given tight controls on information. There have been past false reports regarding its leaders, but the fact Kim has no clear successor means any instability could present a major international risk.

Asked about how any North Korean political succession would work, O’Brien said, “The basic assumption would be maybe it would be someone in the family. But, again, it’s too early to talk about that because we just don’t know what condition Chairman Kim is in and we’ll have to see how it plays out.”

Trump said he had asked Kim about the succession in the past but declined to elaborate.

With no details known about Kim’s young children, analysts said Kim’s sister and loyalists could form a regency until a successor is old enough to take over.

FILE PHOTO: North Korean leader Kim Jong Un takes part in a meeting of the Political Bureau of the Central Committee of the Workers' Party of Korea (WPK) in this image released by North Korea's Korean Central News Agency (KCNA) on April 11, 2020. KCNA/via REUTERS

MEETINGS WITH TRUMP

In recent years, Kim has launched a diplomatic offensive to promote himself as a world leader, holding three meetings with Trump, four with South Korean President Moon Jae-in and five with Chinese President Xi Jinping.

China is North Korea’s only major ally. Speaking to Reuters, an official at the Chinese Communist Party’s International Liaison Department expressed the belief that Kim was not critically ill.

Daily NK said Kim was hospitalized on April 12, hours before the cardiovascular procedure, as his health had deteriorated since August due to heavy smoking, obesity and overwork. It said he was now receiving treatment at a villa in the Mount Myohyang resort north of the capital Pyongyang.

“My understanding is that he had been struggling (with cardiovascular problems) since last August but it worsened after repeated visits to Mount Paektu,” a source was quoted as saying, referring to the country’s sacred mountain.

Kim took two well-publicised rides on a stallion on the mountain’s snowy slopes in October and December.

Speculation about Kim’s health first arose due to his absence from the anniversary of the birthday of North Korea’s founding father and Kim’s grandfather, Kim Il Sung, on April 15.

North Korea’s official KCNA news agency gave no indication of his whereabouts in routine dispatches on Tuesday, but said he had sent birthday gifts to prominent citizens.

Kim has sought to have international sanctions against his country eased, but has refused to give up his nuclear weapons, which pose a threat to the United States.

Joseph Yun, a former U.S. envoy to North Korea under President Barack Obama and Trump, told Reuters he believes “something really is quite amiss, quite awry right now in North Korea”.

“It’s worrisome. If he’s seriously ill and he dies, there is no succession plan,” he said. “You could see a huge power struggle, people jockeying for position. Their lives would depend on it.”

Yun said for all its secrecy, North Korea in recent years had been quick to respond to significant foreign news reports and it was noteworthy that it had stayed silent so far.