On his first official visit to Japan since taking office in June, Lee met Ishiba at the premier's residence in Tokyo to discuss bilateral ties between the East Asia neighbours, including closer security coordination with the United States under a trilateral pact signed by their predecessors.

With US foreign policy in flux, Japan and South Korea are finding common ground on trade, defense, and demographic challenges.

A deal with the White House to help Trump revive US shipbuilding offers a risky route to expansion for South Korean yards.