By Sakura Murakami and John Geddie TOKYO (Reuters) -A leadership contest in Japan's ruling party to determine who will take over as prime minister headed to a run-off on Friday, putting a candidate seeking to become Japan's first female premier against a veteran making his fifth leadership bid.

Ishiba defeated economic security minister Sanae Takaichi in a runoff, after the two won the most votes in the first round in a crowded field of nine candidates.

A seasoned defence geek and a nationalist who would be Japan's first woman prime minister will go head-to-head in the final round of a ruling party leadership vote on Friday,