The US has pledged two extra ballistic missile destroyers to help Japan protect itself against North Korea, as tension simmers on the Korean peninsula.
Following a meeting between US Defence Secretary Chuck Hagel and his Japanese counterpart Itsunori Onodera on 6 April, the two countries announced that the warships will be in place from 2017.
"In response to Pyongyang's pattern of provocative and destabilising actions ... I can announce today that the United States is planning to forward-deploy two additional AEGIS ballistic missile defence ships to Japan," Hagel told reporters.
The US fleet in Japan already has five vessels capable of ballistic missile defence.
After the talks with Onodera, Hagel said: "These steps will greatly enhance our ability to defend both Japan and the US homeland from North Korean ballistic missile threats. This move to significantly bolster our naval presence is another action that strengthens our alliance and increases deterrence against North Korean aggression."
The decision is also seen as a sign that Washington is backing its ally in its growing territorial disputes with China.
The Japanese defence minister said: "I'd like to confirm close cooperation between Japan and the United States to address provocative missile launches [by North Korea]."
South and North Korea exchanged artillery fire after a shell fired by Pyongyang fell in Seoul's disputed territory, heightening tensions in the region. Following the firing, Seoul has beefed up security across the country to gear up for any further provocation.
Tensions have remained high over the last few weeks as North Korea continues to test-fire missiles in a show of belligerence against South Korea and the US.
Under the resolutions passed by the UN Security Council, North Korea is banned from launching ballistic missiles.