A former Pentagon official argued against the idea of South Korea acquiring nuclear-powered submarines (SSNs) in a media contribution piece on Friday, citing high costs, operational realities and other challenges.

Dov S. Zakheim, who served as undersecretary of defense from 2001 to 2004, made the case in the piece carried by The Hill, a US media outlet, as he pointed out a continuing debate in South Korea over whether the country should possess SSNs.

The debate has gained traction in recent years as North Korea has been doubling down on its pursuit of stronger naval capabilities, including underwater attack drones and submarine-launched ballistic missiles. But a Seoul-Washington nuclear pact limits the use of nuclear materials for military purposes.

Zakheim said that it was only in April when President Yoon Suk Yeol and US President Joe Biden reached an agreement that entails the establishment of the Nuclear Consultative Group and the United States' pledge for an enhanced American nuclear presence around the Korean Peninsula.

"Were South Korea to attempt to evade its long-standing commitment to Washington to concentrate all its nuclear-related efforts solely for civilian purposes, it would undermine the spirit of the Biden-Yoon agreement and create a serious split between the two countries -- from which only the North Koreans would benefit," he said in the piece.

He pointed out that if Seoul were to have a new submarine program, it would have to build at least three vessels to ensure one boat operates on station at all times. Three submarines are likely to cost more than $10 billion once logistics support is taken into account, he added.

"For South Korea to field a credible fleet, it would have to ensure that two subs are always on station, meaning that both the total number of boats to be acquired, and their corresponding costs, would have to double," he said. "It is not at all clear that the government can increase its already significant defense spending levels by additional tens of billions of dollars."

In addition, Zakheim cited "good" operational reasons why Seoul should continue to acquire conventional submarines.

"The waters around the Korean peninsula are relatively shallow, which favors the employment of quiet conventional subs," he said.

During a confirmation hearing last week, South Korea's Joint Chiefs of Staff Chairman-nominee Adm. Kim Myung-soo noted the "sufficient" utility of nuclear-powered submarines, but stressed the need to consider it "carefully."

Zakheim is currently a senior adviser at the Center for Strategic and International Studies and vice chairman of the board at the Foreign Policy Research Institute. (Yonhap)