William Hagerty, the new U.S. Ambassador to Japan, vowed Thursday to maintain ¡°ironclad¡± bilateral security ties in the face of North Korea¡¯s escalating nuclear and missile threats and said he expects Tokyo to assume a greater role in the decades-old alliance Washington regards as a cornerstone of regional stability.

¡°I expect to see us strengthening our position in the face of the increasing threat here in this region, and I also expect to see further involvement of Japan and further responsibility and authority of Japan,¡± he said, speaking to reporters after arriving at Narita airport near Tokyo in late afternoon.

¡°Our partnership with Japan is ironclad and our ability to defend ourselves becomes even stronger as we work more closely together,¡± he said.