NEW DELHI — The Japan-India security agreement signed recently marks a significant milestone in building Asian power equilibrium. A constellation of Asian states linked by strategic cooperation and with shared common interests is becoming critical to instituting stability at a time when major shifts in economic and political power are accentuating Asia's security challenges.

What Tokyo and New Delhi have signed is a framework agreement that is to be followed by "an action plan with specific measures to advance security cooperation" in particular areas, ranging from sea-lane safety and defense collaboration to disaster management and counterterrorism. How momentous this Oct. 22 accord is can be seen from the fact that Japan has such a security agreement with only one other country — Australia.

Tokyo, of course, has been tied to the United States militarily since 1951 through a treaty designed to meet American demands that U.S. troops remain stationed in Japan even after the American occupation ended. Today that treaty — revised in 1960 — is a linchpin of the American forward-military deployment strategy in the Asian theater.