"During a cabinet meeting, it was decided to open an extraordinary session of the parliament on 4 October," Kato told reporters.
Incumbent Prime Minister Yoshihide Suga announced early September his decision not to run for the head of the ruling Liberal Democratic Party (LDP), which means his resignation as head of government as well.
Four people are bidding for the post — vaccination minister Taro Kono, former Foreign Minister Fumio Kishida, former Interior Minister Sanae Takaichi and the LDP's executive acting secretary general Seiko Noda.