One of South Korea’s wealthiest tycoons is saying he believes his country should go nuclear, in what appears as a riposte to President Trump’s search for compromise with President Putin on Ukraine and also to calls by South Korean leftists for a deal with North Korea.

Chung Mong-joon, an heir, with his brothers and sister, to the Hyundai empire, says it “does not make sense to deploy tactical nuclear weapons in Europe and not on the Korean peninsula, where the security situation is more serious.”

Mr. Chung, who inherited the controlling stake in the world’s largest shipbuilder, Hyundai Heavy Industries, spoke out Tuesday at Washington even as leaders of NATO countries were responding with alarm to the agreement reached between America and Russia in talks in Saudi Arabia to negotiate a settlement on the war in Ukraine. President Trump initiated the process by phone with President Putin.

While Mr. Trump has suggested NATO countries should rely far more on themselves for their own defenses than on American largesse, Mr. Chung called for “an Asian version of NATO.” He suggested calling it the Indo-Pacific Treaty Organization.

“More and more experts and leaders say they need to think about Asia’s collective security system,” Mr. Chung said. “The United States and its allies and partners must also show a resolute commitment to deter the military adventurism of North Korea, China, and Russia.”

Mr. Chung spoke at Johns Hopkins University’s School of Advanced International Studies after donating funds for an “MJ Chung distinguished professor” chair at the university, from which he earned a doctorate years ago. He is founder and honorary chairman of one of Seoul’s leading think tanks, the Asan Institute of Policy Studies, which posted his speech on its website.

Mr. Chung did not say specifically whether South Korea should produce nuclear weapons or persuade its American ally to redeploy nukes in the South, from which the first President Bush withdrew them in 1991. He did make clear, though, that it’s time to bring them back.

“The U.S.-ROK alliance has remained ironclad for nearly half a century,” he said. “The United States made this happen during the Cold War by deploying its military and tactical nuclear weapons to the Korean Peninsula. In 1991, Russian President Mikhail Gorbachev withdrew 10,000 tactical nuclear weapons from Europe, and U.S. President George H.W. Bush withdrew more than 1,200 tactical nuclear weapons from the Pacific region, including more than 100 in South Korea.”

Mr. Chung’s remarks synthesized the thinking of many South Korean conservatives, disturbed by Mr. Putin’s policies long before he ordered Russian troops to invade Ukraine three years ago. The opposition Democratic or Minju party, leading the move to impeach and oust Korea’s conservative president, Yoon Suk-yeol, would like to renew talks with North Korea’s leader, Kim Jong-un, even though he is calling for getting rid of American troops and bases. About 28,500 American troops are in the South, where they engage in regular training exercises with South Korean forces.

A former member of South Korea’s national assembly, Mr. Chung once had presidential aspirations and assisted his late father, the founder of the Hyundai empire, Chung Ju-yung, who formed his own minor party and ran for president in 1992. Mr. Chung is the sixth of his father’s eight sons, each of whom, along with one sister, got a slice of the pie. The eldest surviving brother, Chung Mong-koo, was bequeathed Hyundai Motor, ranked among the top 10 automotive groups in global sales and market share.

At 73, once the chairman and now honorary chairman of Hyundai Heavy Industries, Mr. Chung seemed just as concerned about China as about Russia.  “Over the past decade, China has exerted economic and diplomatic coercion against Japan, the Philippines, Australia, and Canada,” he said.

Adding to the sense of urgency is that North Korea persists in hyping its own nuclear threat. Pyongyang’s Korean Central News Agency quoted a foreign ministry spokesman castigating Washington’s “outdated and absurd plan of ‘denuclearization,’ which is now getting more impossible and impracticable even practically and conceptually.”

That statement came seemingly in response to the declaration by Secretary Rubio and the foreign ministers of Japan and South Korea, meeting at Munich, that they are committed to the North’s “denuclearization.” Mr. Trump, who earlier had called the North “a nuclear power,” did not refer to “denuclearization” when talking to Mr. Putin.