Kim, who assumed power from his late father in December, spoke for 20 minutes at a rally of thousands to commemorate the 100th anniversary of the birth of his grandfather, the country's founder Kim Il Sung
"We should strengthen the People's Army in every way we can," Kim said.
Kim, who is in his late 20s, avoided any references to Friday's national embarrassment of a botched $1 billion rocket launch that had world leaders on edge, South Korea's Yonhap News Agency said.
The country ignored United Nations' and various international diplomatic warnings against the missile launch and is now facing consequences, Yonhap said.
Among them is the nullification of a U.S. aid deal for 240,000 tons of food in exchange for a suspension of missile testing.
Kim said North Korea was "strong and prosperous," but depends heavily on foreign aid, The Washington Post said.
The Choson Sinbo, a pro-North Korean newspaper based in Japan, said North Korea was likely to conduct a nuclear test if Washington cuts off food aid, Yonhap reported.