The escalating territorial disputes in the Pacific between China and America’s allies create an ever-more-urgent need for U.S. sea power. But even as China rapidly expands and modernizes its navy, the Trump administration has not proposed enough funds to maintain America’s maritime advantage. Beginning with the coming 2019 federal budget, the president and Congress must commit to funding a full, modern fleet—or risk ceding essential U.S. and allied interests.

American sea power has secured the Pacific since the end of World War II, assuring safe and open trade, while defusing conflict throughout the region. Maintaining a powerful navy for these ends is hardly an American innovation: No great state or empire has ever retained its status without pre-eminent sea power. The histories of Athens, Venice, Spain, Holland and England show that losing control of the oceans leads ineluctably to losing great-power status.

The rapid growth and improvement of China’s naval forces is the major challenge to American sea dominance today, and likely for the foreseeable future. Retired Capt. James Fanell, former director of intelligence for the U.S. Pacific Fleet, stated in 2015 that China’s combat fleet will reach 415 ships in 2030. Beijing is particularly focused on adding submarines, amphibious vessels and small surface combatants. The buildup demonstrates China’s clear intention to dominate in coastal regions and amphibious operations—domains in which the U.S. has pre-eminence today.

As Adm. Phil Davidson, nominated to lead the U.S. Pacific Command, told the Senate in April: China “is no longer a rising power but an arrived great power and peer competitor.” He added that “China has undergone a rapid military modernization over the last three decades and is approaching parity in a number of critical areas; there is no guarantee that the United States would win a future conflict with China.”

The White House has proposed expanding the U.S. Navy to 355 ships, but its plan is too slow and underfunded. The full fleet would not be complete until 2050 at the earliest. Although President Trump proposes to dedicate $20 billion for new ship construction in 2019, and about the same in constant dollars in each of the next five years, the Congressional Budget Office estimates the project requires an additional $6.6 billion a year over the next 30 years. Without increased funding, the fleet will be smaller in three decades than it is today, and China’s navy could surpass it by 2030.