It's called "leading from the middle" and is a concept that's catching on as the United States repositions America's military forces in the Pacific and Asia to meet the threats of the 21st century.

For years, the U.S. has been "leading from the front," a time-honored military principle, taking charge of alliances, coalitions and partnerships. That has spawned allegations, especially during the administration of President George W. Bush, that the U.S. was "unilateral" in its approach to security.

Today, the U.S. is seeking more often to lead from the middle, relinquishing the role of leader to an ally or partner and easing U.S. forces into supporting positions. Under this concept, American military leaders look for opportunities to get allies and friends to step up and take charge while the U.S. assumes a backup and reinforcing role.

Secretary of Defense Robert Gates referred to that idea when he told Army cadets at West Point in April: "Just about every threat to our security in the years ahead will require working with or through other nations. Success in the war on terror will depend less on the fighting we do ourselves and more on how well we support our allies and partners in the moderate Muslim world and elsewhere."

The U.S., for instance, is gradually turning over to South Koreans the responsibility for defending their nation, with U.S. forces stationed in Korea pulling back into supporting positions. American troops will thus be freed to respond to contingencies elsewhere.

In the well-traveled waterway through the Straits of Malacca on the western end of the South China Sea, the U.S. has urged Indonesia, Singapore and Malaysia to take the lead in securing the strait against pirates and terrorists. Those nations have been able, through coordinated air and sea patrols, to reduce piracy. The U.S. is equipping five to 10 radar sites each in Indonesia, Malaysia, Thailand and the Philippines to help track ships.

U.S. special operations forces have been assisting the armed forces of the Philippines in the southern reaches of that island nation to battle Abu Sayyaf terrorists. Filipino and American leaders insist that Filipinos are doing the fighting while Americans are advising.

The U.S. Navy's maritime strategy, drawn up under Adm. Michael Mullen when he was chief of naval operations, includes a provision similar to leading from the middle. It calls for "expanded cooperative relationships" in the "maritime domain for the benefit of all."

In particular, the strategy says: "Although our forces can surge when necessary to respond to crises, trust and cooperation cannot be surged. They must be built over time."

Mullen, who is now chairman of the Joint Chiefs of Staff, was traveling this week to Indonesia, Singapore, the Philippines and South Korea, where he was expected to discuss America's supporting role in security.

The concept of Asian nations taking the lead in security, although just being put into practice, is rooted in the Nixon or Guam Doctrine. President Richard Nixon, during a stopover in Guam in 1969, said the U.S. would "furnish military and economic assistance when requested" to Asian nations under attack but that the U.S. would "look to the nation directly threatened to assume the primary responsibility" for its defense.

Japan was an early collaborator, gradually taking over responsibility for its self-defense in the 1970s. Prime Minister Zenko Suzuki announced in 1981 that Japan would defend its sea lanes out to 1,000 miles. Thus U.S. forces stationed in Okinawa and elsewhere in Japan moved into a supporting role and were freed for duties elsewhere.

When the United Nations sent a peacekeeping mission to East Timor in 1999, Australians took control of the operation while the U.S. supported it with aircraft, communications and supplies. Adm. Dennis Blair, at that time leader of the Pacific Command, said the U.S. need not be in charge of every combined operation in Asia.

Two years ago, Adm. William Fallon, then commander of the Pacific Command, was in Medan, Indonesia, to discuss security in the Straits of Malacca with Indonesian naval and police officers. After an initial briefing, an Indonesian officer said somewhat diffidently, "Admiral, we really don't know why you are here. This is our problem and, with our neighbors in Singapore and Malaysia, we can take care of it."

From the look on his face and the tone of his voice, Fallon was clearly pleased. "It's your neighborhood," he replied, "and you should do it yourselves. If we can help, please let me know."

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