Foreign Minister Taro Aso officially declared his candidacy Monday for the Liberal Democratic Party's presidential election, throwing his hat into a ring where Chief Cabinet Secretary Shinzo Abe is already expected to win by a landslide.

At a news conference to announce his candidacy for the Sept. 20 poll, Aso stressed that his campaign would focus on mending the disparities between cities and rural areas.

Aso said that 81 percent of the population lives in Tokyo or other large cities while just 19 percent reside in rural areas.