U.S. Pacific Fleet Commander Adm. Scott H. Swift addresses a conference on Wednesday in Canberra, Australia. Swift said if the United States lost access to international waters claimed by China in the South China Sea, it would have far-reaching implications beyond military. (AP Photo/Rod McGuirk) (Rod Mcguirk/AP)

The United States has long pushed allies to rely less on its huge military forces and to spend more on their own defense. Now a conservative government in Australia, wary of China, is planning an extensive arms buildup.

Prime Minister Malcolm Turnbull has committed to raising defense spending in five years to the equivalent of 2 percent of the economy in perpetuity, a big increase that could influence the balance of power in the Pacific region, experts say.

The decision is an example of how China’s economic and military rise is forcing allies that have long relied on U.S. defense spending to re-evaluate.

Chinese nuclear and diesel submarines have been tracked in the eastern Indian Ocean in the past two years, according to James Brown, a military analyst at the University of Sydney. The more frequent operation of Chinese warships in waters close to Australia is a factor behind the plan to increase defense spending, which had fallen to its lowest level relative to the economy since the eve of World War II, he said.

“The Chinese navy is getting more sophisticated and operating further from home,” Brown said in an interview. “Everyone is looking to increase their influence in the region.”

Australia plans to double the size of its submarine fleet, build nine frigates to hunt submarines, and buy eight spy planes and 72 F-35A fighter aircraft. New anti-ship missiles and transport aircraft would be added as well.

The Australian ships and submarines will be equipped with weapons and other systems similar to those used by the U.S. and Japanese navies, which should improve compatibility with those forces.

A stronger Australian navy would please U.S. naval commanders, who want more firepower to offset the Chinese buildup in the South China Sea, where China’s decision to construct bases on disputed islands has raised fears of an inadvertent clash.

The commander of the U.S. 7th Fleet, Vice Adm. Joseph Aucoin, last month publicly urged the Australian government to conduct naval patrols within 12 nautical miles of the occupied islands — a test of international sovereignty that the Chinese government would probably regard as provocative.

Australia’s new defense minister, Marise Payne, was noncommittal about the suggestion.

Like the other main U.S. allies in the region — Japan, South Korea and Taiwan — Australia has the delicate task of balancing its vital China trade relationship with the military threat. China has the largest navy and air force in Asia, and as that nation grows, analysts expect it to seek greater influence in the region.

If a war were to erupt, the Royal Australian Navy would be used to protect the huge ships that transport the country’s minerals northward. Missiles would defend the gas platforms in northern Australia that provide energy for factories across Asia.

Australia plans to upgrade military runways and expand naval ports, in part to make it easier for U.S. military aircraft and ships to visit. China has missiles that can strike U.S. aircraft and ships at their bases in Japan, the headquarters of the 7th Fleet. Analysts say the United States wants to spread its forces across the region to avoid a Pearl Harbor-like attack.

“If you are concentrated like that, you can create an incentive for [the enemy] to hit you fast, early and very heavily,” said Ross Babbage, a former defense adviser to the Australian government.

In many ways the continent of Australia is the perfect military base. It separates the strategically important Indian and Pacific oceans; it has the equipment, supplies and skilled workers needed by forces operating a long way from home; and it has extensive areas of empty land and ocean that can be used for training.

The policy is likely to be good news for American arms manufacturers. Australia was the seventh-largest foreign buyer of U.S. military equipment in 2013 and 2014, according to the Defense Security Cooperation Agency, which oversees U.S. foreign arms sales.

The White House is likely to be pleased, too. President Obama recently complained, in an interview with the Atlantic magazine, that allies sometimes relied too much on the United States. “Free riders aggravate me,” he said.

Richard L. Armitage, former deputy secretary of state under President George W. Bush, has previously criticized liberal and conservative Australian governments for “free riding” on American defense spending. In an email, he praised the Turnbull government’s plan, especially for its navy, although he acknowledged that it may be up to future leaders to execute it.

“This will allow for much better defense of Australia and a much higher degree of cooperation with the United States, should the government of the day in Canberra so decide,” Armitage said.