Joseph Dunford, chairman of the Joint Chiefs of Staff, agreed at the prime minister's official residence that the US and Japan will continue taking concrete steps together to improve defense preparedness and capability, with an eye toward ballistic missile defense.
Before meeting with Abe, Dunford spoke at the Ministry of Defense with his Japanese counterpart, Adm. Katsutoshi Kawano.
On Thursday, U.S. Defense Secretary James Mattis, Secretary of State Rex Tillerson and their Japanese counterparts agreed at their two-plus-two meeting in Washington to work more closely on the issue.
"This is a very important time for security in the region and of course we are mostly focused on the threat coming out of North Korea", Dunford said.
Meeting with Japanese Prime Minister Shinzo Abe in Tokyo on Friday, as part of his ongoing tour of Asia, Dunford said: "The nature of our bilateral relationship, particularly at the military level, is rock solid".
Also Friday, William Hagerty, the new US ambassador to Japan, said he had arrived at a hard time and that the USA wants to work with Japan to "calm the rhetoric" over North Korea.
Tokyo remains on alert against potential military provocations by Pyongyang after North Korea threatened to fire missiles towards the Pacific island of Guam, US territory, which would have flown over Japan.
The U.S.is bound by treaty to defend Japan from outside attacks against the allied country.
Abe also met Friday with William Hagerty, the new American ambassador to Japan.
Hagerty arrived in Japan on Thursday.
Washington has long encouraged Japan to take on more defence responsibility even though the country is militarily constrained by a US-written constitution imposed after the end of World War II.
Dr Narushige Michishita from the National Graduate Institute for Policy Studies said: "If left to its own devices, China might think it could get away with whatever it does, but with the US' and Japan's repeated demonstrations of their commitment, China might have realised it has to be reasonable".