Japanese Prime Minister Shinzo Abe hailed an "historic" success as he and US President Barack Obama signed an agreement on security issues and made progress in bilateral trade talks.
The two countries issued a joint statement saying they oppose attempts to assert territorial or maritime claims by coercion and specifying that their bilateral security treaty covers Japanese islands claimed by China.
They failed to reach a bilateral trade deal that is key to both leaders' agendas. But Abe said they achieved a "key milestone" by making progress on the talks, which they said will inject "fresh momentum" into attempts to reach a 12-nation Trans-Pacific Partnership pact.
US President Barack Obama has reiterated his commitment to the defence of Japan and its territories, including the disputed Senkaku islands which are claimed by Japan and China.
During a state visit to Japan, Mr Obama reaffirmed that existing US defence treaties with Japan would be honoured, but urged peaceful dialogue with China over the islands, called Diaoyu in Chinese.