This opinion piece originally appeared in The New York Times. 

Over the past 15 years, China has expanded its once-minimal military presence in the South China Sea into a significant one. Beijing has laid claim to nearly all of the strategic waterway, a vital shipping lifeline for the global economy that is rich in energy and fishery resources. China has used nonmilitary assets such as its Coast Guard, fishing vessels and maritime militia to bully its neighbors, blockade their ships and build Chinese military bases on disputed islands.

America is partly to blame. It has condemned China’s behavior, but, eager to avoid escalation, has consistently refrained from standing up militarily, which has only further emboldened Beijing. A new approach is needed. The United States must take real action to strengthen alliances and confront China before it eventually takes control of this hugely important body of water without firing a shot. 

Like any unchallenged bully, China has become increasingly aggressive. Last month, Chinese Coast Guard personnel attacked a Philippine supply vessel with axes and other crude weapons — Manila says a Filipino sailor and several others were injured — in one of the worst acts of violence between China and its rivals in the South China Sea in years. The incident took place near the Sierra Madre, a rusting World War II-era ship that the Philippines had beached 25 years ago at Second Thomas Shoal to assert its territorial claim. The shoal lies about 120 miles off the Philippine island of Palawan and is well within the nation’s exclusive economic zone.

China also had past territorial confrontations in the South China Sea or other waters on its periphery with Vietnam, the United States, Australia, Japan and Taiwan. In 2012, China took control of the disputed Scarborough Shoal from the Philippines, and run-ins between China and the Philippines have grown in number and intensity in recent years. In late May, President Ferdinand Marcos Jr. of the Philippines warned that any Filipino deaths caused by a “willful act” by a foreign force in the South China Sea would be “very close to what we define as an act of war.”

Concern has grown in Manila, Beijing and Washington that tensions in the South China Sea — perhaps even more than Taiwan — could trigger a conflict with China. These fears are overblown. I study Chinese military strength and strategy, and I’m convinced that if the United States were to take a more assertive stance in the South China Sea, Beijing would be likely to back down to avoid a war it knows it would lose.

China may enjoy military advantages in a potential conflict with Taiwan, which is just off the mainland. But its position is less secure in the South China Sea. Over the past 15 years China has built more than two dozen military outposts on disputed islands. Among the largest — at Mischief Reef, Fiery Cross Reef and Subi Reef — there are air strips, fighter jets, radar systems, and laser and jamming equipment. But so far China lacks sufficient antiaircraft and anti-ship missile systems in the region to deny U.S. forces the ability to operate, which leaves the Chinese bases vulnerable to air and naval bombardment.

And the South China Sea is vast — about half the size of the continental United States. The Sierra Madre is around 800 miles from the Chinese mainland. A conflict there would require the People’s Liberation Army to mount joint air and naval resupply operations and to refuel its fighters across great distances — something it has never done and is not equipped for.

If the Philippines is in the fight, treaty obligations would trigger the participation of the United States, which would have access to nine Philippine air and naval bases, greatly enhancing its already considerable ability to project military power in the region. China does have “carrier-killer” ballistic missiles based on its mainland. But U.S. carriers could still send fighters into parts of the South China Sea from outside the range of those missiles. In conjunction with land-based fighters operating from the Philippines, the United States could gain crucial air superiority over a Chinese surface fleet.

China has spent huge sums on its aircraft carrier program and has two in operation, with two more in development. But those still cannot rival the number or capabilities of nuclear-powered U.S. carriers, which are larger, support more aircraft and need to refuel only about every 20 years. China’s carriers need to be refueled about every six days. And learning how to effectively conduct carrier operations takes time; the Chinese have only just begun.

It’s telling that China has been careful to use Coast Guard and civilian vessels in its encounters with neighbors rather than hard military assets — the latter would signal an escalation that Beijing is not yet willing to embark on.

But there is another very good reason China is unlikely to risk war with the United States: It doesn’t need to. Its brinkmanship and use of nonmilitary assets to intimidate its Asian neighbors has been more than enough to take China from almost no military presence in the South China Sea in the late 2000s to a significant force today.

America should call China’s bluff and press its military advantage. This could include escorting Philippine resupply vessels headed to Second Thomas Shoal or even conducting some supply missions itself or with allies like Australia and Japan. This would send China the powerful message that its intimidation will no longer go unchallenged, while allowing Manila to remain visibly in the lead but part of a more enduring coalition. To save face for China, Washington could present operations like these as exercises or training to minimize pressure on Beijing to respond.

Manila is a strategically vital player in America’s regional competition with China. The United States and the Philippines should strengthen their alliance to allow for more U.S. bases in the Philippines and a stronger U.S. commitment to help defend against Chinese incursions into Philippine waters. Closer relations could also make it easier for the United States to resupply Taiwan from Philippine bases during a conflict with China and open the door for enhanced military cooperation with other South China Sea nations, whose fear of an unrestrained Beijing may be deterring them from taking that step. If China determines that its provocations are likely to draw in the United States, it might begin to moderate its behavior .

Of course, anything is possible — Beijing may respond with a full-on military escalation, a daunting prospect that should not be taken lightly. But that risk is low for a Chinese military whose own doctrine is to avoid any war in which victory is not ensured.

Neither U.S. option — standing up to China or backing down — is attractive. But unless the United States asserts itself, China will continue chipping away with its tactics of bluster and intimidation until its military presence in the South China Sea becomes so dominant that it no longer fears war.

The United States can re-establish a favorable balance of power, but it must act now.