The United States Navy has been shrinking for decades and is now at levels last seen in the 1930’s. Politicians on both sides of the aisle say they want to reverse that trend. But is a larger Navy really affordable?

Today’s Navy has 273 active duty ships—14% fewer than were afloat on 9/11. During his 2012 presidential campaign, Mitt Romney proposed a plan to get the Navy to 350 ships. Many of this year’s Republican presidential candidates have called for rebuilding lost naval capacity as well. But making the Navy larger and stronger Navy is actually a bipartisan position. The Obama administration’s budget calls for getting to a 308-ship Navy by 2022 and growing it to 321 ships in 2028.

This is not just politicians trying to sound macho. A strong Navy is necessary to deter bad actors and protect American interests around the world. The defense experts serving on the bipartisan National Defense Panel called for a Navy between 323 and 346 ships, and perhaps higher if threats continue to increase. The Heritage Foundation’s 2015 Index of U.S. Military Strength judged the number of ships needed to counter global threats at 346. Bottom line: strategic needs justify fielding a Navy of roughly 350 ships, and there is bipartisan support for the endeavor.

But the question remains: Is a 350-ship Navy affordable?

To answer that, we must first look at the current shipbuilding budget. The Fiscal Year 2015 shipbuilding budget is $16 billion and the Navy has requested $16.6 billion for FY 2016. While a significant amount of money, this represents only 3% of the total defense budget and less than one half of one percent (0.41%) of total federal spending. From this perspective, the government should be able to manage its naval needs.

What would it take to get to 350 ships? The Navy plans to build nine to 10 ships per year. The Romney plan proposed 15 new ships per year—approximately 50% more. Assume that a 50% increase in shipbuilding would cost approximately 50% more. The Congressional Budget Office estimates that the Navy’s current shipbuilding will cost $18.9 billion annually (more than the Navy has budgeted). Using the CBO’s higher numbers, a 15-ship-per-year budget could cost as much as $28.4 billion annually.

Critics may argue that shipbuilding is not the only cost of 350-ship Navy. More ships require more sailors to operate them, more fuel to power them, and more work to maintain them. But remember that the current Navy goal is to get to 308 ships, with a plan to actually reach 321. A 350-ship Navy is only 9% larger than the current 321-ship plan. A larger Navy fleet would require a higher operations and personnel budget, but it is a manageable increase, and not deal-breaker.

Those higher costs provide increased—and much-needed—capacity. A larger fleet will fulfill the needs for the Navy’s presence around the world with reduced stress on the fleet. More ships means each hull can reduce its deployment time, maintenance work can be performed more regularly and affordably, and individual crews will spend less time out at sea. All of these factors contribute to the long term health and costs of the Navy.

This brings us back to the original question—is this affordable? Assuming the higher cost for shipbuilding, this still only represents 5% of the 2016 defense budget request and only 0.7% of the total 2016 federal budget. While an extra $10-12 billion per year for shipbuilding is a significant increase, many of the presidential candidates—as well as many naval experts—believe that global demands on the Navy are only increasing, making a larger fleet absolutely essential.

A larger Navy will not be cheap, but it is certainly not a fantasy, as some have characterized it. The path to a larger U.S. Navy is both achievable and affordable and is not something that should wait for a future administration. Congress and President Obama should start increasing the Navy’s shipbuilding budget now so that America’s interests are better protected.

-Justin T. Johnson is the senior analyst for defense budgeting policy in The Heritage Foundation’s Allison Center for National Security and Foreign Policy. Brian Slattery, a policy analyst in the Allison Center, contributed to this article.