The United States and South Korea are "moving forward" on the deployment of a US missile defense system in the Asian ally as tensions soar over North Korea's missile programs, the Pentagon said Monday.

Last week, the South Korean government determined that noise and radiation levels were negligible near the site of the Terminal High Altitude Area Defense (THAAD) battery in Seongju, southeastern South Korea.

"They're moving forward," Col. Rob Manning, a Pentagon spokesman, told reporters. "In early May, we got initial intercept capability and they continue to build on that capability."

President Moon Jae-in called for installing four additional launchers for the missile shield, despite earlier reluctance, after North Korea tested its second intercontinental ballistic missile in July.

The THAAD deployment attests to the closeness of the alliance, according to Manning, who described it by the slogan "Gachi Gapsida," or "Let's go together."

The colonel, who recently returned from a two-year stint with the US Forces Korea, said allied joint exercises will proceed as planned later this month.

North Korea denounces the drills as a rehearsal for war, sparking concerns tensions will escalate further following a week of harsh rhetoric between Washington and Pyongyang.

Last week, US President Donald Trump warned the communist nation will be met with "fire and fury" if it continued to threaten his country. In response, the North announced plans to fire ballistic missiles into waters surrounding the US territory of Guam.

"We hope that doesn't happen," Manning said of the North's threatened attack. "As the Department of Defense, our job is to make sure we maintain military options and provide that to the president for consideration...But again, this is a diplomatically led effort at this point." (Yonhap)