Why is the Obama administration cutting funding for two new Coast Guard Cutters while backing a plan to build 20 Navy ships of the same size and cost? Both programs, one for the National Security Cutter and the other for the Littoral Combat Ship, have had their problems, and both services indicate they’ve overcome them, so that can’t be the answer.

The short answer seems to be the Coast Guard, unlike the Navy, is located outside the Defense Department and so falls within the discretionary funding arena where the president can show he’s tough on reducing the deficit even if, in this case, he’s cutting muscle in the name of cutting fat.

While Republicans (and many Democrats with major defense contractors in their districts) are howling about trimming the Pentagon budget 10 percent during the next 10 years, almost no one has complained about the administration’s proposed 4 percent cut in next year’s Coast Guard budget.

The Coast Guard, a hybrid military and law enforcement agency going back to the era of the founders, has always been an institutional orphan in Washington, D.C., presently anchored in the Homeland Security Department. Yet it’s been a highly functional orphan, saving more than 1 million lives over the past two centuries (including 33,000 people rescued during 2005’s Hurricane Katrina), while taking an almost Dickensian pride in being able “to do more with less.” With only 42,000 active-duty members it can expect 1,000 fewer under the administration’s plan.

Even though its coastal security functions were beefed up after 9/11, its aged and rusting high-seas fleet responsible for illegal migrant and drug interdiction (seizing more cocaine than all other government agencies combined), fisheries enforcement, icebreaking, oil spill response and more has been in a decades-long decline. One example: When a dozen Coast Guard Cutters were sent to Haiti after the 2010 earthquake, 10 had serious maintenance problems, two of them needed emergency repairs and one had to be put into dry dock.

Its dozen 378-foot High Endurance Cutters, some dating back to service in the Vietnam War, are supposed to be replaced by just eight new 418-foot National Security Cutters. The first of these modern ships, the Berthold, recently seized $400 million worth of cocaine at sea and will spend this summer patrolling the Arctic Ocean. Two more have now been delivered, but the president’s budget surprised everyone by committing to only six of the eight planned cutters.

Meanwhile, the Navy has built four Littoral Combat Ships of two different designs and is scheduled to receive four more in 2013 out of 20 approved by Congress, with the Navy eventually hoping for 55. These new high-speed shallow draft warships, costing $700 million each — the same as the new Coast Guard Cutters — are designed for anti-submarine, anti-mine and near-shore (or littoral) warfare, basically chasing Iranian speedboats onto the beach.

Some in the administration have suggested the Navy’s Littoral Combat Ships could take up the slack for the Coast Guard Cutters they don’t plan to build. History suggests otherwise. Just after 9/11 the Navy lent the Coast Guard eight 179-foot Coastal Patrol Boats for several years. The Navy warships proved fuel-costly and failed to meet a number of other Coast Guard rescue and law-enforcement requirements.

Still, in Congressional testimony on Feb. 15, Homeland Security Secretary Janet Napolitano defended the administration’s defunding of the last two NSC Coast Guard Cutters, arguing, “We will look at seven and eight in light of what the Navy is doing. … We need to look at what the Department of Defense is doing with respect to their own force to see what we need to be putting in the acquisition pipeline.”

In other words, we may not need new fire department ambulances because the police are getting a new fleet of patrol cars.

The administration’s 2013 budget also calls for decommissioning two of the Coast Guard’s nine remaining High Endurance Cutters. At the same time, the service is years behind in replacing its rusting, broken-down 210- and 270-foot Medium Endurance Cutters, some more than 45 years old.

Its polar icebreaking fleet that included five ships only 30 years ago is down to one, with a second, built in 1976, being retrofitted for renewed service as rapidly changing conditions in the Arctic drive new activities, including shipping and oil-drilling that the Coast Guard is expected to oversee and protect.

Whatever one thinks of the utility of the Navy’s new littoral warships, they should not be used as an excuse to downsize the Coast Guard. In an increasingly crowded world where an unknowable range of maritime threats face us — not only hostile navies but intentional, industrial and natural disasters — it’s crazy to risk crippling the Coast Guard while expecting it to continue providing us safety, security and environmental stewardship at sea. Yet that is what the president’s 2013 budget does.

David Helvarg is executive director of the Blue Frontier Campaign, an ocean conservation and policy group, and author of “Rescue Warriors: The U.S. Coast Guard, America’s Forgotten Heroes.”