WASHINGTON -- The United States is actively considering allowing South Korea to increase the capacity of its ballistic missiles in the face of North Korea's growing military threats, the Pentagon said Monday.

The remark by Pentagon spokesman Navy Capt. Jeff Davis comes a day after South Korean President Moon Jae-in requested a revision to the allies' missile guidelines in a phone call with his US counterpart, Donald Trump.

"Yes, we are working on it," the spokesman told reporters when asked if the Pentagon is reviewing the request. "It is a topic under active consideration here."

He went further to add, "And I would tell you that we would be favorably inclined to do anything which furthers the defensive capabilities of South Korea."

Under the current guidelines, South Korea is prohibited from developing ballistic missiles with a range of more than 800 kilometers and a payload of over 500 kilograms.

But it is now pushing to increase the cap on payloads to 1 ton or 1,000 kilograms.

Moon ordered consultations on such a revision after North Korea launched its second intercontinental ballistic missile on July 28.

"We will always adapt to the threat as it changes," Davis said, adding he does not know of a time line for the revision.

Opponents in South Korea argue a revision could provoke neighboring countries, including China and Russia.

The guideline was first signed in 1979 and revised in 2001 and then 2012. (Yonhap)