President Biden’s summit Wednesday with South Korea’s president, Yoon Suk-yeol, is likely to wind up in a blaze of rhetoric intended to cover the reality that influential Americans with long experience in the region are highly divided on what to do about North Korea. 

Underlining the debate is the sense that Koreans are losing confidence in America’s will to defend them to the hilt if a second Korean War breaks out with North Korea, especially if China and Russia rushed to the North’s defense as during the first Korean War.

“Events have caused Koreans to question, ‘Can we count on the U.S. for extended deterrence?’” the president of the Center for Strategic and International Studies at Washington, John Hamre, told a forum at Seoul sponsored by a Korean think tank, the Asan Institute for Policy Studies.

 “We need to know what it means to take on the astounding capability to be a nuclear weapons state,” Mr. Hamre, talking via a remote link from Washington, said. “If necessary extended deterrence means we’re going to fight side by side up to and including nuclear weapons.” 

Given the skepticism about America’s total commitment to South Korean security, Korean and American policymakers have reportedly worked out an elaborate statement on “extended deterrence” for Messrs. Biden and Yoon to sign at their summit. 

The language will no doubt be firm and decisive, but it’s expected to avoid definitive answers to two basic questions: Should South Korea develop its own tactical nukes, and should Mr. Biden agree to deploy nuclear warheads to South Korea, from which President George H.W. Bush withdrew them in 1991? 

Differences of opinion suffused the musings of senior officials, past and present, as they talked about the rising threat of North Korea. The bottom line was that we have to act fast — but how? 

President Trump’s national security adviser and the ambassador to the United Nations under President George W. Bush, John Bolton, in a keynote address to the gathering, evinced no doubt about the first question. 

“The United States should redeploy tactical nuclear weapons on the peninsula,” he said, buying time “for South Korea to think long and hard as to whether it wants its own nukes.” 

Aside from agreeing on the need to strengthen the American-South Korean alliance, though, other Americans with long backgrounds in South Korea appeared divided and uncertain as to what to do about North Korea’s nuclear program. No one seemed to agree totally with Mr. Bolton on the wisdom of South Korea going nuclear with its own or America’s nukes. 

“No” and “no” was the simple response of a retired general, Walter Sharp, who commanded American forces in Korea for three years between 2008 and 2011, when asked those questions.

That response did not mean, however, that he wasn’t concerned about the North. 

“I worry not only about their nuclear capability but also their conventional capability,” General Sharp said, noting the North has 6,000 artillery pieces, 4,000 of which were close enough “to hit this room.” Nor did he think we necessarily have the luxury of time before the North attacks. 

“Escalation could be very rapid and hard to control,” he said. “The plans now in place to respond to North Korean attack could be very, very rapid.”

A former American ambassador to Korea, Sung Kim, said he was sure “extended deterrence” would be “a very prominent topic for our two leaders.” Mr. Biden’s national security advisor, Jake Sullivan, he noted, had “already indicated that what comes out of the summit will very clearly convey our sense of commitment, extended deterrence commitment” to South Korea. 

Like General Sharp, though, Mr. Kim, who’s now serving concurrently as ambassador to Indonesia and also America’s special envoy on North Korea, demurred when asked about nukes for South Korea. In fact, he said, the notion of implanting American nukes on South Korean soil was not on the table. Nor did he think there would be any talk about South Korea fabricating its own warheads even as “North Korea is continuing to provoke in an unprecedented way.” 

A one-time North Korean diplomat who in 2016 defected to the South from the North’s embassy at London, Tae Yong-ho, who is now a member of the South’s national assembly, had a unique proposal for expanding extended deterrence. 

America, Mr. Tae said, should take the lead in forming a nuclear defense for the region against the combined power of China and Russia as well as North Korea. He was not confident, though, that Washington would go for it. “We have to ask,” he said, “if America is willing to have a regional nuclear state or not.”