US waits, Iran warns of 'war' as Seoul weighs Strait of Hormuz deployment

As South Korea weighs sending troops to the Strait of Hormuz, the United States and Iran are each sending competing messages to Seoul. Washington says it is waiting for South Korea's decision, while Tehran has warned it would treat any Korean involvement against Iran as participation in war — deepening Seoul's dilemma.

Yoo Ji-hoon, a research fellow at KIDA, said Sunday that while the United States formally says it is waiting for South Korea's decision, the stance carries an undercurrent of political pressure. "Given that President Donald Trump has publicly expressed dissatisfaction with South Korea's limited contribution to Hormuz security, the message appears to implicitly demand a more active role," Yoo said.

That dynamic is also linked to Trump's decision to share on social media a Washington Post column arguing that the United States should pressure South Korea to sell Cheongung-II air defense systems to Ukraine. The episode reflects a broader trend in Washington toward expecting South Korea to take on greater responsibilities in international security — not just on the Korean Peninsula, but in the Middle East and Ukraine as well.

Yoo added that Washington's assessment of South Korea's alliance contributions could ripple across other bilateral defense issues. "With major Korea-US defense and security matters — including defense cost-sharing, the transfer of wartime operational control, extended deterrence and nuclear-powered submarines — all likely to be discussed at the same time, how the US perceives South Korea's contributions to international security could influence those other alliance issues as well," he said. The implication is that Washington is increasingly inclined to evaluate Seoul's alliance commitments through a comprehensive lens.

Iran, meanwhile, has sent a stark warning. A senior Iranian official said that if South Korea becomes involved in operations against Iran in the Strait of Hormuz, Tehran would regard it as participation in war.

That warning has brought the safety of any deployed South Korean assets into sharp focus. Particularly concerning is the recent shift in the pattern of US-Iran hostilities: clashes have expanded beyond the strait itself to include airstrikes on each other's warships and oil tankers in surrounding waters, raising serious doubts about whether non-combat assets could be kept safe.

South Korea's Ministry of National Defense had previously maintained that a deployment would only be possible after the Strait of Hormuz stabilizes and the safety of South Korean service members is guaranteed. However, Trump's increasingly public pressure — combined with a ripening atmosphere for North Korea-US dialogue — appears to have prompted Seoul to more actively consider a deployment as a way to strengthen its role in the alliance.

Yang Wook, a research fellow at the Asan Policy Research Institute, said a troop deployment could give South Korea greater standing to speak up within the alliance. "If a deployment becomes reality, it would send a message that South Korea stands with the United States and help Seoul avoid being sidelined — or 'Korea-passed' — in North Korea-US talks and other diplomatic processes," Yang said.

Assets under consideration for deployment include the P-8A maritime patrol aircraft, capable of monitoring vast stretches of ocean and detecting and striking submarines and surface vessels; an explosive ordnance disposal unit; and the ROKS Soyang, an 11,000-ton replenishment vessel that supplies fuel, ammunition and other logistics to naval fleets.

Following Iran's warnings, however, the government is reportedly reviewing whether to exclude the replenishment vessel from the deployment and reduce overall troop numbers. Seoul's challenge of responding to US requests for military support while avoiding diplomatic friction with Iran is growing more acute.