Gates will meet with Japanese Defense Minister Toshimi Kitazawa and other leaders of the Japanese government, including Prime Minister Naoto Kan, the Pentagon said in a release.
"We will use the trip to discuss how best to address recent security developments in the region -- including North Korean provocations -- and to further develop our long-term agenda for strengthening and deepening the bilateral alliance," Pentagon spokesman Geoff Morrell said. "The visit will underscore the centrality of the U.S.-Japan relationship for addressing regional and global challenges, now and in the years to come."
Gates spent four days in China and will travel to South Korea Friday.
Before leaving for Japan, Gates visited the headquarters of China's strategic missile command, the 2nd Artillery Corps.
Gates said discussions with Chinese leaders will help advance military-to-military relationships between the two countries.
"The discussions were productive and set the stage for taking the military-to-military relationship to the next level," Gates told reporters.
"What came across to me is both the military and civilian leadership seemed determined to carry this relationship further and build upon it," he said. "Are there those who have issues with it? Possibly, but I didn't meet them on my trip, and I'm very encouraged going forward."
Gates called discussions with Gen. Jing Zhiyuan, 2nd Artillery Corps commander, "very candid" and said Jing accepted an invitation to visit the U.S. Strategic Command at Offutt Air Force Base, Neb., later this year.
"This is part of the step-by-step process of building this relationship," Gates said.
Gates said U.S. and Chinese leaders discussed "their no-first-use policy, about command and control and several other subjects."