The United States is unlikely to assist South Korea in constructing nuclear-powered submarines due to its commitments to the AUKUS pact with Australia, according to US Defense Secretary Lloyd Austin, speaking at the Shangri-La security dialogue in Singapore.

The United States signed the AUKUS pact with Britain and Australia in 2021 to share nuclear-powered submarine technology and to sell at least three Virginia-class boats to Australia in the 2030s. 
  
Several other US allies, including South Korea, have expressed interest in involvement. 

During the security summit on Saturday, Austin was asked about how he would respond to a direct South Korean request for help in obtaining nuclear submarines, he said it would be "very very difficult" for Washington to accommodate that "on top of what we do right now." 
  
"(AUKUS) is no small endeavor," he said. "We just started down this path with Australia. (It's) highly doubtful that we could take on another initiative of this type anytime in the near future." 

Containing China

AUKUS's two-stage security agreement aims to counter China's influence in the Asia-Pacific region to contain Beijing. This will mark the first time since the 1950s that Washington has shared nuclear-propulsion technology, with the previous instance being with Britain.
  
In addition to the submarines, the pact includes a second technology-sharing "pillar" that has garnered interest from New Zealand and Japan.
  
On the sidelines of the Shangri-La Dialogue on Friday, New Zealand's Defense Minister Judith Collins said, "We believe that AUKUS is actually a good addition to regional security," adding that New Zealand had enquired about the second pillar. 
  
"We've had no actual invitation to join it but it is something that we are certainly looking at," she said. 
  
Australian Defense Minister Richard Marles mentioned that he could envision the involvement of other countries in the future. However, he emphasized that the current focus is on the US-UK-Australia trio making progress on the submarine projects, which are expected to span several decades.

On that note, earlier this month, South Korea engaged in discussions to join a military technology pact between the United States, the UK, and Australia in the AUKUS anti-China alliance, the country's defense minister said on May 1.

"During today's meeting, we also discussed the possibility of partnering with AUKUS Pillar Two," Shin Won-sik said.

Pillar Two is dedicated to developing advanced technologies, including artificial intelligence, to deploy in war capabilities such as drones, hypersonic missiles, and other hardware.