US Defense Secretary James Mattis has referred to America's “ironclad” commitment to defend South Korea a day after Seoul signed a joint peace declaration with the North in which both sides vowed to work toward a denuclearized Korean Peninsula and formally end the Korean War.

The announcement came in a statement issued Saturday by Pentagon’s chief spokesperson Dana White, saying that Mattis made the pledge while discussing the outcome of the inter-Korea summit with his South Korean counterpart, Song Young-moo.

Dana White said:  "Secretary Mattis reaffirmed the ironclad US commitment to defend the ROK (Republic of Korea) using the full spectrum of US capabilities."

White also noted that the two military chiefs “expressed serious commitment to a diplomatic resolution that achieves complete, verifiable, and irreversible denuclearization of North Korea, as reflected in multiple United Nations Security Council Resolutions.” 

The renewed commitment by the US military comes on the same day that American President Donald Trump spoke with his South Korean counterpart Moon Jae-in, stating afterwards that the time and location for his planned summit with North Korean leader Kim Jong-un is being worked out.

The development comes as US analysts are cited in press reports as saying that the Korean peace talks will likely weaken the two levers that Trump has used to pressure Kim to come to the bargaining table.

The New York Times wrote in a Saturday column:  "A resumption of regular diplomatic exchanges between the two Koreas will inevitably erode the crippling economic sanctions against the North, while Mr. Trump will find it hard to threaten military action against a country that is extending an olive branch."