The status of North Korean leader Kim Jong Un’s health is still unclear, despite reports that he could be in dire condition following a cardiovascular surgery. U.S officials told NBC News that Kim has been absent from public view after the operation, and the dictator may be incapacitated.

National Security Adviser Robert O’Brien said Washington is keeping a “close eye” on reports or information about Kim’s health.

"We're monitoring these reports very closely," O’Brien told Fox News on Tuesday. "As you know, North Korea is a very closed society."

South Korea has so far said there are no signs to point towards Kim being in a health crisis.

"No unusual signs have been identified inside North Korea," Kang Min-seok, a spokesperson for South Korean President Moon Jae-in said. "There is nothing we can confirm with regard to Chairman Kim's alleged health problem."

Kim, 36, could be at risk for major health issues, as he is overweight and has been pictured smoking. His former sushi chef claimed that Kim is also a heavy drinker. On April 15, the dictator missed the celebrations of his grandfather’s birthday, raising speculation about his health. Kim’s grandfather, Kim Il Sung, founded North Korea in 1948.

Kim Jong Un became the Supreme Leader of North Korea after his father, Kim Jong Il, passed away in 2011. He has continued his family’s antagonism towards the West, frequently shooting off rockets and pursuing an illicit nuclear program. Kim, however, has managed to strike a friendship with President Trump, with the two leaders meeting several times over the past two years.

North Korea and the U.S. had been engaged in negotiations over the country’s nuclear program, with Pyongyang wanting sanctions to be reduced on its economy in exchange for a possible path to denuclearization. Negotiations on the issue have been stalled since October, when North Korean and U.S. diplomats met in Sweden.

If Kim Jong Un is in dire condition, his sister, Kim Yo Jong, 31, could be one of the top candidates for the country’s next Supreme Leader. Kim Yo Jong has frequently accompanied her brother on international trips and is in charge of propaganda affairs