The US will increase cooperation between its troops stationed in the Indo-Pacific and other militaries to deter armed conflict with China in the Taiwan Strait and South China Sea, analysts said.
The assessment after the US Air Force in South Korea attended joint military exercises in Singapore for the first time in five years.
According to the US Forces Korea (USFK), six F-16 fighter jets along with 90 aircraft maintainers from the American base in Osan, south of Seoul, were sent to Singapore to take part in a three-week annual joint military exercise.
It said the Commando Sling 23 drills, held from November 6-24, enabled the US and Singaporean air forces to "build aerial communication, evaluate tactics, increase interoperability, and improve alliance capability".
"Bilateral training provides Osan pilots, maintenance personnel and other supporting professionals opportunities to engage with and learn from our allies," said US Air Force Lieutenant Colonel Cory Ferrer, commander of the 36th Fighter Squadron based in South Korea.
"When we go to exercises such as Commando Sling, we practise combat agility while demonstrating the strength and necessity of partnerships."
It is rare for the USFK, dedicated to defending Seoul against Pyongyang, to operate outside the Korean peninsula and take part a in a drill in a country other than South Korea or the US.
The last known time was in 2018 when six F-16s from Kunsan Air Base in Gunsan, on South Korea's west coast, joined Commando Sling.
Stephen Nagy, a professor of politics and international studies at International Christian University in Tokyo, said the exercise showed America's capacity to work with like-minded countries across Southeast Asia.
"It sends the message that [US] forces in Korea can be deployed not only to Southeast Asia but also perhaps across the Taiwan Strait in the case of the Taiwan contingency," Nagy said.
"This is an important message to revisionist powers within the region that the United States forces based in either Korea or Japan or other places may actually be able to be deployed in other zones of conflict."
The USFK's participation in the joint drills comes amid rising tensions in the Taiwan Strait and South China Sea.
On Monday, the People's Liberation Army accused the US of being "the biggest threat to peace and stability" in the South China Sea shortly after littoral combat ship, the USS Gabrielle Giffords, conducted combined operations with the Philippine Navy in the disputed waters, and passed near Second Thomas Shoal. It is one of the disputed atolls in the Spratly Islands that has seen recent clashes between Beijing and Manila over resupply missions conducted by the Philippines.
Last week, Chinese defence ministry spokesman Senior Colonel Wu Qian also called a US plan to deploy intermediate-range missiles in the Indo-Pacific next year to deter a conflict over Taiwan a "dangerous trend", adding that it would "seriously undermine regional peace and stability".
"China is firmly opposed to it and will resolutely counter-attack. It needs to be emphasised that the Taiwan issue is purely China's internal affairs and [China] does not tolerate any external interference," Wu said.
On Wednesday, a US P-8A anti-submarine patrol aircraft passed through the Taiwan Strait. The PLA's Eastern Theatre Command said it sent fighter planes to monitor the aircraft's passage.
Bruce Bennett, a defence researcher at the US-based think tank Rand Corporation, said placing US combat aircraft in East Asia meant Washington was deploying "rapid response forces" designed to deal with any sudden local conflict development.
"US air forces based in the ROK [Republic of Korea] could be used to support Taiwan should China ever decide to invade Taiwan. Hopefully that will never happen," Bennett said.
"Fortunately, air forces are relatively easy to deploy. Therefore other US combat aircraft would fly within days to cover any of the US fighters deployed from South Korea and also to support US allies elsewhere in the theatre."
Collin Koh, a senior fellow at the S. Rajaratnam School of International Studies in Singapore, said the USFK's ties with Southeast Asia aligned with America's "Agile Combat Employment" concept introduced in 2022, with Washington's aim to improve deterrence by supporting joint all-domain operations.
"Such a concept allows the US forces in the theatre to move across areas more flexibly to support operations where needed. In this way, forces deployed to a certain area aren't confined to that area, and can be employed to respond to crises in an adjacent area at a distance," Koh said.
"This complicates the adversary's calculations but at the same time, it also will depend on regional partners and allies providing needed access."
Choo Jae-woo, a professor of Chinese studies at Kyung Hee University in Seoul, said the USFK had more "strategic flexibility" in operating within the region than other US troops in East Asia, thus giving it a larger role in war scenarios with China.
"Because of Japan's pacifist constitution, the US Forces Japan must focus on Japan's national defence and has limitations in exercising strategic flexibility," Choo said.
"South Korea is in a different situation," he said. "Pyongyang can take advantage of the USFK's absence to attack the south, but Seoul's military would be enough to defeat those offences."
Kim Hyun-wook, a professor at the Korea National Diplomatic Academy, said while the USFK's main focus was the Korean peninsula, its recent joint exercise with Singapore pointed to preparation against a possible war in the Taiwan Strait and the South China Sea.
"If the confrontation in the South China Sea got any more severe, there is a chance that a part of the USFK would be rushed to the region," Kim said. "Any Taiwan contingency is Japan and Korea's contingency. It would likely expand into a regional war."
Nagy said the US had been pushed to prepare its troops in the region over concerns about North Korea and Taiwan, as well as an increase in coordination between authoritarian states such as China and Russia.
"I do expect more integrated coordination of all US forces … to deal with the emerging challenges that are coming as a result of increased militarisation throughout the region by China," Nagy said.
"That means we're going to see more interoperability, more integration of all US assets … to deal with the challenges within the region."