Communist icon Fidel Castro on Friday called on North Korea and the United States to avoid confrontation and reminded both sides of their "duties" towards peace.
"If a war breaks out there, there would be a terrible slaughter of people" in both North and South Korea "with no benefit for either of them," Castro wrote in a front-page article in Granma, the Communist Party's newspaper.
Now that the North Korean government "has demonstrated its technical and scientific advances, we remind them of their duties with those countries that have been their great friends."
Castro urged North Korea to remember that "such a war would affect ... more than 70 percent of the planet's population," and decried "the gravity of such an incredible and absurd event" in such a densely populated region.
Castro said the present crisis presents the most serious risk of a nuclear war since the 1962 Cuban missile crisis, a two-week standoff between the United States and the Soviet Union over placing nuclear missiles in Cuba.
The "duty" to avoid the conflict is also in the hands of Washington "and of the people of the United States," Castro said.
If a war breaks out, President Barack Obama's second term "would be buried in a deluge of images that would portray him as the most sinister personality in the history of the United States."
Castro, 86, handed over power to his brother Raul in 2006 but remains influential in Cuba and among leftists worldwide.
In his article, the Cuban leader recalled "the honor" of meeting Kim Il-Sung, the founder of the North Korean regime and grandfather to current leader Kim Jong-un.
The late North Korean leader, who died in 1994, was a "historic figure, notably brave and revolutionary," Castro wrote.
Castro also wrote that North Korea "has always been friendly with Cuba, as Cuba has been always and will continue to be" friendly with North Korea.
Castro writes an occasional column titled "Reflections of Comrade Fidel" that runs in state media. This is his first column since June 2012.
North Korea, incensed by UN sanctions and South Korea-US military drills, has issued a series of apocalyptic threats of nuclear war in recent weeks.
On Thursday the North Korean army said it had received final approval for military action, possibly involving nuclear weapons, against the threat posed by US B-52 and B-2 stealth bombers taking part in the joint drills.