A South Korean senior official has rekindled debate over the U.S. commitment to that nation's defense, bringing up the possibility of the U.S. rolling back its nuclear umbrella if former President Donald Trump is reelected.

Kim Tae-hyo, South Korea's deputy national security director, said in a Seoul forum Tuesday the reelection of Trump could "weaken a U.S. nuclear umbrella" designed to protect South Korea from North Korean aggression.

"Trump as candidate can be seen as pursuing transactional benefits in terms of the South Korea-U.S. alliance," Kim said, according to news reports. "It is not unlikely that he would suggest negotiating defense cost-sharing or the deployment of U.S. strategic assets from a cost perspective."

Skepticism about America's willingness and capability to protect South Korea from a North Korean nuclear attack has grown among South Koreans as North Korea's nuclear and missile programs become increasingly sophisticated. A recent poll by South Korea's Institute of National Unification revealed that 66% of respondents supported the country having its own nuclear weapons.

Concern over commitment

Gary Samore, former White House coordinator for arms control and weapons of mass destruction during the Obama administration, said Kim's remarks reflect widespread concern among U.S. allies.

There is a concern that "Trump, if reelected, would pursue policies that will weaken U.S. alliances around the world, including in Europe and East Asia," Samore told VOA Korean Wednesday via email.

"In the case of Korea, Trump might seek to resume summit diplomacy with Kim Jong Un and make concessions that weaken the U.S.-ROK alliance, as he did at the Singapore summit in June 2018," Samore said. ROK stands for Republic of Korea, the official name for South Korea.

According to the joint statement released after the 2018 summit, Trump "committed to provide security guarantees" to North Korea, while the North Korean leader reaffirmed "commitment to complete denuclearization of the Korean Peninsula."

"However, I think it's premature to predict exactly what policies President Trump will adopt toward Korea if he is reelected," Samore added. "There are too many uncertainties, including, for example, who President Trump appoints for his top foreign policy and defense positions."

Michael O'Hanlon, director of foreign policy research at the Brookings Institution in Washington, told VOA Korean Tuesday via email the South Korean official's assessment of Trump is justifiable.

"I think the official is correct," O'Hanlon said, adding Trump could take steps to address this concern. "I do not know if he will."

'Treat us properly,' says Trump

Trump has often complained that U.S. allies do not pay the U.S. enough for bases and troops used in their defense. In an April interview with Time magazine, Trump said, "I want South Korea to treat us properly," suggesting he would demand that South Korea pay more for the American troops stationed there.

But Frederick Fleitz, who served as chief of staff of the National Security Council in the Trump White House, told VOA Korean by phone Tuesday that Trump's reelection is not likely to affect the U.S. nuclear umbrella.

Making clear that he was speaking for himself, not for Trump, Fleitz said the former president "was a strong friend of Japan, South Korea and Taiwan when he was in office last time and he'll be a strong friend again."

"Why would there be such a big change in a second Trump term when he didn't do that in the first term?" Fleitz asked. "The second Trump administration, concerning South Korea, will be countering the threat from North Korea and this new axis relationship between China, Russia, North Korea and Iran."

Fleitz stressed there is no evidence to suggest Trump would link the defense cost-sharing with offering a nuclear umbrella, adding discussions on how much South Korea pays for U.S. troops in South Korea will not be a "deal breaker" for the second Trump administration.

"It is an issue that will be resolved among friends," he said. "The security threats in the region are so severe — I think that's what the U.S. will focus on."

Redeployment of nukes

Robert Peters, a fellow for nuclear deterrence and missile defense at the Heritage Foundation, told VOA Korean Tuesday via email it is "far more likely" that America's extended deterrence commitment to South Korea would strengthen during a second Trump term.

Peters said a second Trump administration could consider redeploying U.S. tactical nuclear weapons to the Korean Peninsula, due to the threats coming from North Korea and China.

"I think a second Trump administration would field SLCM-N [nuclear-armed, sea-launched cruise missiles] in the near term and potentially reintroduce American nuclear weapons to South Korea as a means to assure the ROK, deter North Korea and strengthen regional stability," said Peters.

Vice President Kamala Harris, the Democratic presidential nominee, is widely expected to inherit incumbent President Joe Biden's Asia policies should she win the election.

The Biden administration is not considering the redeployment of tactical nuclear weapons to South Korea. In 1991, the U.S. withdrew from South Korea all its nuclear weapons, roughly 100 in number, according to some studies.

"The United States does not assess returning nuclear weapons to the Indo-Pacific as necessary at this time," a State Department spokesperson said in an emailed statement on May 31 in response to a VOA Korean inquiry. "The United States has no plans to forward deploy nuclear weapons to the Korean Peninsula."

In April 2023, Biden and South Korean President Yoon Suk Yeol adopted the Washington Declaration, in which the U.S. declared that its commitment to the defense of South Korea will be backed by the full range of U.S. capabilities, including nuclear.

During this week's high-level security talks between the U.S. and South Korea, the Biden administration reiterated its commitment to defend South Korea with nuclear weapons if necessary to deter attacks from North Korea.

"We reaffirm the U.S. extended deterrence commitment to the ROK using the full range of U.S. defense capabilities, and that any DPRK [North Korea] nuclear attack on the United States or its allies and partners is unacceptable and will result in the end of that regime," Bonnie Jenkins, U.S. undersecretary of state for arms control and international security, told reporters after Wednesday's talks.

VOA Korean contacted the Trump campaign and asked what Trump's stance is on the U.S. nuclear umbrella offered to South Korea, but did not receive a reply by the time this article was published.