NEW DELHI — By coincidence, Prime Minister Shinzo Abe of Japan and Adm. Timothy J. Keating, commander of U.S. forces in Asia and the Pacific, were in India at the same time last month and for the same reason — to entice India into closer security relations with their respective nations.

Then President Bush, in Australia last week for an Asia-Pacific summit gathering, conferred at length with Prime Minister John Howard on Iraq and on wider issues of security in Asia. And even as they spoke, warships from Australia, India, Japan, and the U.S., plus Singapore, were training together in the Indian Ocean.

Taken together, Australia, India, Japan and the U.S. are forging an informal defensive pact based on shared national interests and democratic values. An Indian commentator, Sudha Ramachandran, has called it a "quadrilateral axis of democracy" or "quad."

While he was here, Abe was quoted in the Hindustan Times as saying: "A broader Asia, that broke away geographical boundaries, is now beginning to take a distinct form." He called it an "open and transparent network."

China was quick to assert that the quad was an attempt to contain Beijing's influence. Chinese contended that Japan in Northeast Asia, Australia in Southeast Asia, and India in South Asia were lined up against them, with U.S. military power in the Pacific Command as backup.

Senior officials in all four nations were equally quick to deny they were engaged in a concerted plot against China. Keating told reporters here: "There's no — let me emphasize no — effort on our part or any of those other countries, I'm sure, to isolate China, to put them in a closet."

Indeed, each nation has sizeable trade relations with China that leaders are anxious not to jeopardize. Moreover, each has domestic political restraints that would crimp an anti-China stance. In India, for instance, nationalists rail against the possibility that India would be drawn into a security posture subordinate to the U.S.

No one in authority is talking about a formal alliance like the North Atlantic Treaty Organization, or NATO. Rather, officials indicated that they are building atop existing U.S.-Japan and U.S.-Australia treaties, plus newly fashioned U.S.-India security relations.

Despite the constraints, leaders of the four nations have expressed concern that China's military modernization may eventually constitute a threat. They are walking on a razor's edge between engagement and deterrence as they hedge against that day.

In India, another commentator, Prem Shankar Jha, has written that "epochal changes in the international order" after 9/11 include India's emergence as an economic power and a spurt in international respect for its democracy.

Jha contended the major powers have felt a need "to broaden the base of the informal consensus among larger countries to cope with the progressive disintegration of the international order, the spread of new threats that require collective action, the rapid decline of U.S. hegemony, and its need for friends after its misadventure in Iraq."

For its part, India has been lessening its reliance on Russia for weapons; remains unhappy with China's alliance with its archrival, Pakistan; and still has border disputes with China. Indian leaders have expressed unease over China's gradually increasing presence around the Indian Ocean.

In Australia, Minister of Defense Brendan Nelson justified Canberra's reliance on collective defense in a recent speech. He noted that dangers from weapons of mass destruction, the prospect of failing states, and transnational crime and terror required joint action. He was worried that the U.S. would turn to isolationism after Iraq.

Nelson said his nation of 20 million people was limited in providing for its own security. "We need to work with other people," he said. Collective defense, however, must be realistic, not just for show and talk. Australians, he said, "are pragmatic. We don't generally believe in traveling dinner clubs."

In Japan, strategic thinkers have pointed to open hostility from North Korea, barely concealed hostility from South Korea, and anxiety over long-term threats from China despite recent moves by Beijing to reduce the antagonism.

Tokyo has begun to enhance its modest self-defense force and to revise its constitution to permit Japan to take part in a collective defense. Nonetheless, for the foreseeable future, Japan will remain dependent on the U.S. for much of its conventional and for its entire nuclear defense.

For the U.S. Pacific Command, the guideline for collective action set by several recent commanders has been: "No nation is so big it can go it alone, and no nation is too small to contribute."

Richard Halloran is a Honolulu-based journalist and former New York Times correspondent in Asia. His column appears weekly in Sunday's Focus section.