SEOUL, South Korea — Confronting growing doubts about whether a planned meeting between President Trump and Kim Jong-un, North Korea’s leader, would take place, a South Korean official said Monday that there was a “99.9 percent” chance of it happening.

Speaking to reporters aboard South Korea’s Air Force One, Chung Eui-yong, a national security adviser to the country’s president, Moon Jae-in, played down recent reports that Mr. Trump had become nervous about meeting Mr. Kim in Singapore next month for a historic summit meeting.

“We have perceived none of that,” Mr. Chung said, countering a New York Times report that cited Trump administration officials as saying that Mr. Trump has begun pressing his aides and allies about whether he should take the risk of proceeding with a meeting with Mr. Kim.

Mr. Chung also denied that when Mr. Trump called Mr. Moon over the weekend, Mr. Trump asked why the North’s recent public statements seemed to contradict private assurances that Mr. Moon had conveyed after he met Mr. Kim on the inter-Korean border in late April.