White House National Security Adviser Robert O'Brien reportedly said on Tuesday that the United States doesn't know what condition North Korean leader Kim Jong-un is in, and will have to see how events unfold.

The remarks come after CNN reported earlier in the day that Kim was in "grave danger" following surgery.

According to Reuters, O'Brien told reporters that the Trump administration is keeping a close eye on reports regarding Kim's health. 

In footage aired by CNN, O'Brien said it is too early to discuss who would succeed Kim when asked about how political succession would work in North Korea.

The security adviser said the basic assumption would be that maybe it would be someone in the family, but it's too early to say anything because the U.S. just doesn't know Kim’s condition and it will have to see how it plays out. 

O'Brien said in an interview with Fox News that the U.S. is keeping a close eye on developments in North Korea, noting it is a very closed society. 

He said that North Korea is parsimonious with the information that they provide about many things, including Kim's health, so the U.S. is  monitoring those developments closely.