Japan and the United States have agreed to update 16-year-old guidelines governing their security alliance so as to address growing concerns over North Korea's nuclear development, global terrorism, cyber warfare and other 21st century threats.
The accord came in so-called "two-by-two" consultations held here on Thursday between Japan's Foreign Minister Fumio Kishida and Defence Minister Itsunori Onodera and their US counterparts John Kerry and Chuck Hagel.
The guidelines, to be ready by end next year, will determine the roles of the Japanese Self-Defence Force and the US military in the alliance for the next 15 to 20 years.
The talks took place amid reports that Pyongyang may have restarted a reactor capable of producing enough plutonium to make one nuclear bomb a year.
A US research team in Washington said satellite imagery showing the release of hot water indicated that the reactor was in operation.
The International Atomic Energy Agency urged North Korea last month to halt nuclear activities, including restarting the reactor.
In separate talks with Mr Onodera earlier on Thursday, Mr Hagel called North Korea's missile programme an "unmistakable threat" to not only Japan, but also South Korea and the US, and said it was important that the three countries cooperate to deal with it.
The defence secretary said after the consultations that "our goal is a more balanced and effective alliance".
In their 10-page joint statement, both sides confirmed the location of a second X-band US missile defence radar system at Kyogamisaki airbase in western Kyoto prefecture to be installed within the next year to complement another system in northern Aomori prefecture.