WASHINGTON -- US Defense Secretary Jim Mattis vowed Tuesday to bolster the defense of Guam against North Korea's ballistic missile threats.

At a congressional hearing, Mattis was asked by Guam Delegate Madeleine Bordello whether the US territory in the Western Pacific is adequately defended from "theater missile threats" and how he plans to strengthen the defense systems already in place.

"We will continue bolstering them to keep pace with the threat out of North Korea," the secretary said. Bordello had noted the presence of the THAAD missile defense system on her island, as well as B-2 and B-52 bombers. Guam is also home to a major US Air Force base.

"Besides the THAAD system we also keep the Aegis Ballistic Missile Defense US Navy warship in the waters out there. We can always reinforce that," Mattis said. "We also have several of those ships in Japanese waters right now and they can move back and forth to include coverage of Guam in the mobile way that comes to our Navy."

The Pentagon is looking at "all the systems," including the land-based component, Aegis Ashore, to ensure future protection of the Pacific area, he said.

Last summer, Pyongyang threatened to fire ballistic missiles toward Guam amid a heated war of words between its leadership and US President Donald Trump. Tensions ran high as North Korea staged three intercontinental ballistic missile tests and its sixth and most powerful nuclear test last year.

Mattis sounded the alarm over the pace of weapons development around the world.

"Nuclear delivery system development over the last eight years shows numerous advances by Russia, China, and North Korea versus the near absence of such activity by the United States," he said, "with competitors and adversaries developing 34 new systems as compared to only one for the US -- the F-35 aircraft." (Yonhap)