TOKYO — US Defense Secretary Ash Carter's first visit to Japan has been cast as a major step forward in cementing a new era for bilateral defense cooperation as the allies look to complete a revision of US-Japan defense guidelines April 27, just before the 2+2 US-Japan Security Consultative Committee scheduled the following day.

Following a Wednesday n April 8 meeting with Japan Defense Minister Gen Nakatani, Carter and Nakatani confirmed several key issues. important for different reasons for each side.

For the US, Japan will push to shift forward in relocating the US Marine Corps' Futenma Air Station to a different location on Okinawa, a move that has met attracted a lot of resistance from locals but is central to the US forward-basing strategy as part of its "Asia pivot," reinforcing its the US presence in East Asia to contain China. Carter advocated that , a policy advocated by Carter when he served as deputy secretary of defense in 2011-13.

Regarding the commitment, Nakatani stated that Japan "will steadily" implement the relocation … "to maintain deterrence and reduce the burden of Okinawa in hosting bases based on an agreement reached during the two-plus-two talks in 2013. It is also part of the US rebalancing policy and very important," he told reporters.

Meanwhile, both sides affirmed that they will oppose any efforts to use force to change in the status quo by force in the East China Sea and elsewhere. They refrained from referring to China directly.

Updating the 18-year-old guidelines has been a priority for the two allies in the face of a rising with the rise of a nuclear threat by North Korea, China's bid for great power status and so-called "peaceful" regional hegemony, and the massive and concomitant economic, trade, technological and strategic changes that have occurred since the mid-1990s.

The new guidelines are extremely important as they implicitly endorse US support for Japan's July 1, 2014, Cabinet Resolution allowing Japan to reinterpret its constitution to allow it to engage in the nation limited rights of collective self-defense in some circumstances.

The guidelines are designed to promote "seamless" defense cooperation without preset geographical limits covering 1) peacetime and gray zone incidents falling short of military attacks on Japan; 2) situations that significantly influence Japan's peace and security, allowing Japan to provide ammunition and refuel warplanes headed for conflict zones; 3) situations that pose a clear danger to Japan through an attack on a close ally; and 4) an attack on Japan.

For the third scenario, cooperation will extend to ballistic missile defense and perhaps actions such as forcible inspections of foreign ships, for example.

The This week's talks mark considerable progress between the allies who had been working hard to resolve, in particular, Japanese fears about seamless cooperation that could lead leading to potential entanglements with US interventions in conflicts in which Japan had no direct stake, and settling the specific details in which the US would come to Japan's aid in "gray zone" situations not directly involving an armed attack on Japan.

In an interview, Hiroshi Imazu, chairman of the Liberal Democratic Party's Research Commission on Security, told Defense News that there are almost "no gaps" in the positions between the sides as both entered the final stages of negotiations.

However, Ken Jimbo, a leading Japanese security expert and professor at Keio University, said that there are still perceptual gaps between the two sides.

The United States views the alliance with Japan in terms of its strategic utility and its role in the supporting its US long-term competitor strategy in dealing with China, he said. The US, Jimbo said, wants Japan as a reliable, flexible basing partner. , who is flexible. Japan, on the other hand, is still worried about the realities of how the US will support Japan in so-called gray-zone conflicts.

"I guess we can indeed call the visit quite successful, but I have a slight doubt. Japan has a difference in emphasis, and we can call this a slightly divergent view," he said.

Jimbo said the definitions , realities and implications of "seamless" cooperation were necessarily still in the mix and will change as new technologies and situations emerge. In terms of current strategic technologies, including space technologies, the US wants Japan's support for full-domain access across in the five domains of land, sea, air, space and cyberspace to counter China's access-denial A2/AD strategy.

However, Japanese thinking is more practical and local; Japan is more worried about under what circumstances, and how , and how much, and when will the US would come to its aid the aid of its closest Asian ally if that ally is threatened, especially in a policing situation involving paramilitary or police forces, Jimbo said.

"Both sides have a different capacity for escalation in dealing with gray-zone disputes. The US thinks about area denial, precision strike and air superiority. Japan has different priorities," he said.

Against this, Carter is reported to have told Nakatani he will strongly oppose any unilateral coercive action that undermines Japan's administration of the Senkaku Islands, for example. This signals , so signaling that the US is sensitive to Japanese concerns about countering China's strategy of using paramilitary, police and fishing fleets to encroach on and pressure the territories of surrounding nations in region as it prosecutes its strategic aims.

On top of this, Both sides also have made substantial progress in cooperation with the now strategically critical fourth and fifth domains, space and cyberspace, agreeing and that Japan would establish a new Japan-US military working group to boost cooperation in space situational awareness and maritime domain awareness to counter China.