Updated

Japanese Prime Minister Shinzo Abe is vying for his third re-election as the ruling party leader next week, extending his stay in power to work on his long-cherished ambition — to revise his country's war-renouncing constitution.

Abe reportedly has already secured about 70 percent of support from parliamentarians of the Liberal Democratic Party, and clinching the re-election would allow him up to three more years to work on a possible charter change. He has to tackle the economy and other priorities too.

He faced his only challenger, Shigeru Ishiba, a former defense minister, during Friday's debate, which could be the only public discussion before the Sept. 20 vote.

"I will take on the task of revising the constitution, a postwar challenge that has never been achieved, in order to open a new era," Abe told the nationally televised event.

The 63 year-old Abe, prime minister since December 2012, is poised to become Japan's longest-serving leader with a historic third term.

A revision to the U.S.-drafted 1947 constitution has been the party's decades-old pledge that none of Abe's predecessors could achieve. It includes Abe's grandfather, former Prime Minister Nobusuke Kishi, who also saw the constitution as humiliation following Japan's World War II defeat.

Abe said earlier this week that he hoped his party could submit a draft revision to a parliamentary session later this year. His coalition government holds a two-thirds supermajority in both houses.

Abe reportedly has the support of least five main factions of the Liberal Democrats, securing some 300 of the 405 votes, as well as many others among local party members.

Abe has survived a series of scandals, including cronyism allegations against him his wife Akie, and has maintained support ratings of around 40 percent, considered high for a government that already lasted five years and eight months.

Lawmakers in Abe's party say they have supported him for continuity in Japan's diplomatic and economic policies as the country faces regional security concerns and an unpredictable American leader.