Prime Minister Shinzo Abe plans to announce his candidacy Sunday for the Liberal Democratic Party leadership contest next month as he looks to secure a third consecutive term as LDP chief, a senior party lawmaker said Wednesday.

During his visit to Kagoshima Prefecture over the weekend, Abe is expected to express his intention to run in the election scheduled for Sept. 20, according to the lawmaker.

The prime minister has been touring the country in an apparent attempt to broaden his support base among rank-and-file party members in a bid to defeat his rival, former Defense Minister Shigeru Ishiba, who has already thrown his hat into the ring.

The LDP presidential election effectively determines the nation's next prime minister, as the ruling party controls a majority in both chambers of the Diet.

Abe is believed to be in the lead, with support from five out of seven intraparty factions. Victory would give him another three-year term, putting him on track to become Japan's longest-serving leader ever.

Abe and Ishiba are expected to officially register their candidacies on Sept. 7, setting off the official campaign period.

Debates are expected on a number of issues, including amending the Constitution — in particular, its war-renouncing Article 9.

Abe also faces the challenge of how to regain public trust amid persistent allegations of favoritism leveled against him in connection with a pair of school building projects carried out by people with ties to him or his wife.