American Defence Secretary Chuck Hagel has said the US will send two ballistic missile defence destroyers to Japan.
The ships will join several US warships already stationed in Japan by 2017.
Mr Hagel made the announcement during a visit to Tokyo as part of efforts to counter recent missile tests by North Korea.
He also addressed territorial disputes between China and its neighbours, saying Chinese authorities should have "respect for their neighbours".
In February Mr Hagel had already announced the expansion of its missile defence capabilities in Asia, with an additional radar planned in Japan that could track any missile launched from North Korea.
In his comments on China's territorial disputes with other East Asian nations, he drew a parallel with Russia's actions in Ukraine's region of Crimea, which has been annexed by Russia.
"You cannot... redefine boundaries and violate territorial integrity and sovereignty of nations by force, coercion and intimidation, whether it's in small islands in the Pacific or large nations in Europe," he said.
Relations between China and Japan are currently under strain over a territorial row involving islands in the East China Sea known as the Senkaku islands in Japan and the Diaoyu islands in China.
It is also involved in another dispute over islands in the South China Sea, a region in which the Philippines, Brunei, Malaysia, Vietnam and Taiwan all have claims.