Lt. Gen. Xavier Brunson testifies during an Armed Services hearing to examine his nomination to be the commander of the United Nations Command, Combined Forces Command and United States Forces Korea on Capitol Hill in Washington on Tuesday. (AP-Yonhap)

Maintaining 28,500 American troops in South Korea is "essential," the nominee for US Forces Korea commander has said, amid concerns that former President Donald Trump could weigh a USFK troop reduction should he return to the White House.

Lt. Gen. Xavier Brunson staked out his position in written answers to lawmakers' questions ahead of his Senate confirmation hearing on Tuesday. If confirmed, he would lead the South Korea-US Combined Forces Command, United Nations Command and USFK.

"A minimum force level of 28,500 is essential for USFK to sustain and operational plans depend on that baseline of capability and capacity," he wrote.

"Moreover, the ROK has a declining birthrate that will impact the size of their military in the next 20 years. If confirmed, I will review all noted challenges and their potential effects on USFK's operational plans," he added, referring to South Korea by its official name, the Republic of Korea.

Concerns have persisted that if reelected, Trump, known for his America-first credo, could consider various options, including a troop cut or pullout, to pressure Seoul to pay more for the stationing of American troops in South Korea.

Responding to lawmakers' question about USFK's missile defense needs, Brunson stressed the need to use layered defense systems and prelaunch capabilities and develop "cost-effective" technologies.

"We must explore lasers and other electromagnetic ways of defeating ballistic and cruise missiles in a cost advantageous manner," he said. "If confirmed, I will advocate for increased missile defense assets and advanced pre-launch capabilities with USINDOPACOM, ROK, and United Nations Command member states."

USINDOPACOM stands for the US Indo-Pacific Command.

Commenting on motivations for the North's pursuit of nuclear arms, the nominee said that North Korean leader Kim Jong-un's "enduring strategic priority" likely is to achieve a "level of military force and deterrence that assures the survival of the Kim regime, international relevance, nuclear capabilities development and self-reliance."

He warned that Kim could use nuclear weapons in an attempt to deter the United States or UNC member states from becoming involved in a conflict on the Korean Peninsula.

"Lastly, Kim Jong-un may view nuclear and chemical weapons as a counter to the US-ROK alliance's significant advantage in conventional air, sea, and land military capabilities," he said.

Brunson noted that Pyongyang has a "robust" chemical and biological weapons capability.

"North Korea has the capability to produce nerve, blister, blood, and choking agents and has several thousand metric tons of them stockpiled," he said.

"North Korea likely could employ chemical weapons agents by modifying a variety of conventional munitions, including artillery and ballistic missiles. Furthermore, North Korea can employ these capabilities in conjunction with nuclear weapons, posing an existential risk to our ROK allies." (Yonhap)