Speculation is mounting about what happened to North Korean leader Kim Jong-un, who has not been seen in public since April 11.

What prompted the guesswork most of all was his failure to make his annual visit to the mausoleum of his late grandfather Kim Il-sung last week. April 15 marked the 108th anniversary of the birth of the communist state’s founder.

US news outlet CNN reported Tuesday that Washington was looking into intelligence that Kim was “in grave danger” after undergoing surgery, citing an unidentified US official with “direct knowledge” of the matter.

Previously, a South Korean internet news outlet reported that Kim was receiving medical treatment at a resort north of Pyongyang after a cardiovascular procedure.

US President Donald Trump told a press briefing Tuesday that he knew nothing about the state of Kim’s health, saying, “I wish him well.”

South Korean officials dismissed reports that something had gone wrong with Kim’s health, saying no unusual signs had been detected in the North to suggest such a thing.

It is extremely difficult to confirm sensitive information about the dictator of the world’s most reclusive regime. But it is certainly unusual that the North’s propaganda machine has kept mum for more than a week since speculation arose about Kim’s health.

Seoul and Washington should keep a close watch on the situation in the North and be prepared for the possibility of a sudden change in leadership.

If Kim -- who took over in 2011 after his father, Kim Jong-il, died of a heart attack -- proves incapable of holding onto the reins of power, the totalitarian regime might be put in disarray, making the regional situation volatile.

President Moon Jae-in’s government seems concerned that its push for inter-Korean reconciliation might be hampered by instability in the North. Since the liberal ruling party secured a dominant majority in last week’s parliamentary election, it has renewed its pledge to strengthen cooperation with the North, speeding up preparations to revive cross-border projects.

But given the possibility that the situation on the peninsula could become volatile -- depending on what happens with Kim’s health -- what the Moon government should do first is to assess South Korea’s security posture and take whatever steps are needed to bolster it.

Above all, it should step up its efforts to conclude the stalled negotiations with Washington on how to share the costs of stationing 28,500 US troops here.

Trump said Monday that he had rejected South Korea’s latest offer because the country is wealthy and should “pay for a big percentage of what we’re doing” to help defend it.

Earlier reports said Seoul had proposed increasing its contribution by 13 percent from the $870 million it paid last year.

US Forces Korea has placed more than 4,000 local employees on unpaid leave since the beginning of April due to the absence of a new defense cost-sharing deal, known as the Special Measures Agreement. The previous accord expired at the end of last year. The massive furlough risks disrupting USFK’s operations and preparedness and undermining the South Korea-US alliance.

Seoul needs to be more flexible on the scope of the SMA and should consider accepting Washington’s demand that it pays for the rotational deployment of an infantry brigade from the US mainland to South Korea.

In return, it might request that the cost-sharing accord be renewed on the basis of multiple years instead of being amended annually.

It is worrisome that the discipline of South Korea’s armed forces is lapsing, as shown in a recent series of embarrassing incidents at the barracks.

An Army corporal is under investigation over allegations that he hit a female captain with a shovel earlier this month. Four noncommissioned officers are suspected of sexually harassing a superior officer last month. A private first class was arrested in early April in connection with a high-profile online sex crime case.

These incidents follow on the heels of civilian intrusions into military bases that prompted concerns over lax discipline.

Stern measures should be taken to tighten military discipline.

The alarmingly loose discipline of South Korea’s military seems to stem from the Moon government’s preoccupation with reconciliation with the North.

A military agreement signed by the two Koreas in September 2018, which bans hostile acts against each other, has weakened South Korea’s military posture while North Korea has continued to make provocations.

The Defense Ministry last week vowed to expedite ongoing reform projects to make the military smaller but stronger and to better deal with nontraditional security threats such as terrorism, natural disasters and epidemics.

It should pay more attention to making sure the military is fully prepared to cope with more immediate security risks.