During its annual conference in Tokyo on Sunday, the ruling Liberal Democratic Party (LDP) rubber stamped a change in party rules that allows leaders to serve three consecutive terms for a total of nine years.

The decision puts Shinzo Abe, who has been in office since December 2012, on a course to become the country's longest-serving leader since the end of World War II. Before he took office, Japan saw six prime ministers in as many years.

At present, LDP rules allow its leaders to serve two straight terms for six years.

Abe will be able to remain in office until 2021 if he can maintain the support of his party and voters.

Challenge still possible

Local media report he may still face a leadership challenge from former LDP Secretary General Shigeru Ishiba.

In Japan's parliamentary system, the ruling party leader generally becomes the prime minister.

Abe, now in his fifth year in office, is Japan's sixth longest serving prime minister since 1945. The record-holder is Eisaku Sato, who led the country for more than seven years from 1964 to 1972. If Abe can hold on, he would surpass Sato in August 2020.

The 62-year-old leader earlier served as premier for a year, during which he was dogged by a string of scandals involving his cabinet ministers, before resigning in September 2007.

A prolonged tenure will allow Abe to focus on a change to the country's post-war constitution, which he previously attempted and failed to achieve.

In particular, he plans to renounce Article 9, which outlaws war as a means to settle international disputes.

mm/jlw (AP, dpa)