President Donald Trump on Tuesday wished North Korean leader Kim Jong Un "good luck" following reports suggesting Kim could be incapacitated following a cardiovascular surgery.

"These are reports that came out, and we don't know," Trump said at a White House press briefing when asked what he knew about Kim's condition.

"I've had a very good relationship with him. I wouldn't -- I can only say this, I wish him well, because if he is in the kind of condition that the reports say, that's a very serious condition, as you know," Trump said. "But I wish him well."

The president added: "I've said it and I've said it many times, if somebody else were in this position right now we would be at war with North Korea ... So I just have to say to Kim Jong Un, I wish him very, you know, good luck."

Speculation about Kim's health first arose after his absence from the April 15 anniversary birthday celebration of North Korea's founding father Kim Il Sung, the grandfather of Kim Jong Un.

Daily NK, a South Korean newspaper that focuses its coverage on North Korea, said late Monday that Kim on April 12 received a cardiovascular procedure at Hyangsan Hospital. The outlet also reported that Kim was recovering in a villa near the hospital.

NBC News, citing American officials, reported early Tuesday that Kim recently had cardiovascular surgery. Some of those officials said intelligence suggests Kim could be incapacitated.

NBC's report seemed to contradict South Korea's presidential office, which told the outlet that Kim "is currently touring provincial areas with his close aides and we do not detect evidences to support speculation about his ill health."

Trump said at the briefing Tuesday night that "nobody's confirmed" the "very serious" reports about Kim's health.

The president said his relationship with Kim has been "very good," which has been to the benefit of the U.S.

"That's not a bad thing, that's a good thing," Trump said. "I'd like to see him be well and we will see how he does. Again, I don't know if the reports are true."