As Donald Trump and Hillary Clinton stepped closer to claiming their parties' presidential nominations on Wednesday, Japanese experts and policymakers are beginning to pay close attention to the U.S. election.

They said the choice of the next American commander in chief is important for Japan, given the overlap of security and economic interests.

On Super Tuesday, the biggest date in the primaries, Clinton won seven of 11 states and Trump did at least as well, as the front-runners padded their leads in the all-important delegate counts that determine the parties' nominees.