The US Navy faces a new threat on the high seas: As potential adversaries spend lavishly to boost their maritime capabilities, we're outgunned for the first time in modern history.

The Pentagon has wisely sought to rectify this imbalance with $2 billion to upgrade and increase to 4,000 the stockpile of Tomahawk anti-ship cruise missiles. The new investment will re-establish US naval dominance over all potential comers.

"These are large investments in the strategic future at the high end, aimed at making sure that our systems have the greatest capability, the greatest lethality … of anybody else," Defense Secretary Ash Carter explained last month as he visited Naval Air Weapons Station China Lake, California.

Skeptics, though, are urging the Navy to abandon this plan and instead develop an expensive new weapons system.

America long dominated the high seas. As the Cold War simmered, the Navy invested in the most cutting-edge anti-ship missiles on the globe. The Tomahawk reigned, a beast of a missile capable of reaching a target as far as 1,000 miles away. Hostile enemy ships didn't stand a chance — and they knew it.

But they were not happy about it. China has been increasing its military spending by an average of 11 percent per year for the past two decades, especially focusing on sea power — "buying, copying and sometimes stealing technology," as Reuters recently observed.

Russia, likewise, is posing a renewed threat, especially under a bellicose Vladimir Putin. The Office of Naval Intelligence recently concluded that Putin seeks nothing less than a restoration of Soviet-era sea power over the next five years. Moscow has invested not only in new submarines and warships but also advanced weapons systems.

Iran, meanwhile, has spent years building up anti-ship missiles, with US warships their unannounced targets. Earlier this year, the Iranian Revolutionary Guard detained American sailors whose boats strayed off course in the Persian Gulf, broadcasting video propaganda of the ordeal. Tehran has also threatened to send warships near American maritime boundaries — a provocation all the more poignant given that the last time the US Navy sank a ship, in 1988, it was an Iranian gunboat.

Erratic North Korea's naval ambitions are also worrisome. Last year, Pyongyang released details of a new high-speed hovercraft armed with missiles capable of targeting ships within a 100-mile range. All in all, more than 70 nations now own a total of more than 75,000 anti-ship missiles.

The Tomahawk is the only weapon that can restore American deterrence at sea. The GPS-powered system boasts 90 percent reliability. It's been used more than 2,000 times in combat, including in 2011, where it played a pivotal role in the NATO-led effort to depose Moammar Gadhafi in Libya. More recently, U.S. forces have fired Tomahawk missiles against the Islamic State group.

The latest Tomahawk is also capable of receiving in-flight target updates to reflect evolving available intelligence. Given the historical difficulty of identifying vessels and determining the level of threat they pose, this cutting-edge technology diminishes the risk of error.

That technology, paired with more precise tracker and seeker capabilities to home in on a moving target, means the latest iteration of the Tomahawk is a "game-changer," as the deputy defense secretary recently said. The missile is so versatile that "it can be used by practically our entire surface and submarine fleet."

Despite these realities, some defense analysts are pushing for a new weapons system. But the major potential alternative to the Tomahawk under consideration, the Long-Range Anti-Ship Missile system, is vastly more expensive and offers only half the range of a Tomahawk.

The LRASM can also be fired only from the air, meaning the Navy would need a nearby runway to use the missile. That's impractical for the western Pacific. Aircraft carriers could work — but equipping a ship for such a weapon can cost hundreds of millions of dollars.

Considering that a timely upgrading and restocking of the Tomahawk will restore our dominance at sea, this push doesn't seem wise.

The Pentagon's proposal is an appropriate response to our new maritime challengers. We can re-establish American dominance at sea at reasonable cost with a larger and more capable stockpile of Tomahawk missiles. The most effective approach to preserving freedom of movement on the high seas is to reinforce our deterrent capabilities.

J. Michael Barrett, a former naval intelligence officer, Fulbright scholar and director of strategy at the White House, is the director of the Center for Homeland Security and Resilience.

More In Commentary