Along the wild and windswept Cape Hatteras National Seashore, man is battling nature again. The U.S. Army Corps of Engineers proposes to stop the collapse of a small inlet crucial to the North Carolina fishing industry by erecting two huge stone jetties at a cost of $100 million.

This planned intrusion in the fragile barrier islands of the Outer Banks has met customary resistance from environmentalists and coastal geologists. But the Oregon Inlet rescue mission faces another snag that may prove as insurmountable as nature: Interior Secretary James G. Watt.

Normally known for his pro-development views, Watt is singlehandedly holding off the multimillion-dollar jetty project by refusing to grant the corps construction permits. One jetty would be anchored on the national seashore, managed by the department's National Park Service, and the other on Pea Island, a national wildlife refuge.

Watt says the law forbids such construction in parks.

"The secretary heard the facts, and he said: God made the barrier islands. God will move the barrier islands. God will do what he wants with the barrier islands. And mortal men have no right to interfere," an Interior Department official said.

Spokesmen for Watt said they never heard him make the remark, but it has circulated as testament to his stand on barrier islands. While battling environmentalists on many issues, Watt has been an ally on protecting the shifting sandy masses created thousands of years ago when glaciers melted away from the East Coast.

The islands, which shield the mainland from sea storms, creep slowly southward with ocean currents, and much development on them is doomed to wash away. Watt supported passage of a 1982 law that halted federal subsidies for construction on 188 barrier islands and beaches.

The curious political currents stirred up by the jetties are concentrated in North Carolina. There Sen. Jesse Helms (R-N.C.) and his arch-rival, Gov. James B. Hunt Jr. (D), have swallowed animosities over their 1984 race for Helms' seat to support the project, with spirited backing from business leaders.

"Just working for the benefit of the state," a Helms aide explained.

With Hunt's support, Helms and Rep. Walter B. Jones (D-N.C.) are drafting legislation to remove two slices of the seashore from Interior Department jurisdiction, just enough for anchoring the jetties, and transfer them to the corps. "This would, shall we say, untie Secretary Watt's hands," the Helms aide said. Jones heads the Merchant Marine and Fisheries Committee, which will handle the bill.

The corps has concluded that the two-mile-long, stone jetties are the only way to save the struggling northern Carolina fishing industry, anchored in the small village of Wanchese on the tip of Roanoke Island south of Nags Head.

About 200 boats frequented Wanchese as few as three years ago, using Oregon Inlet as a passage to beds of flounder, bluefish, trout and sea bass in the Atlantic. The state envisioned the village as a booming commercial fisheries center and invested millions of dollars in a seafood industrial park there.

But nature is reclaiming Oregon Inlet, as it has taken other inlets of the Outer Banks. Relentless ocean currents steadily nibble away the sands of each barrier beach, nourishing those down the coast, and so move the islands south at 10 to 20 feet a year. Oregon Inlet is filling in and is often impassable.

The once-promising seafood park, ready for business last July, has lured only one tenant. Packing houses are moving boats north to Virginia, taking jobs and commerce with them. Those still open have lost three-fourths of their business, said Willie Etheridge III, owner of Willie Etheridge Seafood Co. Only three boats were docked in Wanchese one day recently, he said.

While corps engineers are confident that jetties can stabilize the inlet, halting the natural and economic currents, coastal scientists and Interior Department officials say the corps does not understand what it faces. The federal government tried in vain throughout the 1960s and 1970s to control the barrier island system, said Jay Gogue, chief scientist for the National Park Service in the southeast.

"We drew the line in the sand and said the ocean won't come any further," he said. "We nourished the beaches, replenished the sand dunes along Cape Hatteras, manipulated the seashores. We planted grass on the dunes and fertilized them. We tried to fight nature, and it was costing us a fortune. Very honestly, we weren't able to do it."

The multimillion-dollar bridge carrying the lone highway from Nags Head to Cape Hatteras spans dry land above Oregon Inlet for more than a mile. About 40 miles south, the Atlantic is within 80 feet of the historic Cape Hatteras lighthouse, built 1,800 feet from the sea more than a century ago.

The jetties might keep sand out of the inlet, but they would interfere with the nourishing of beaches to the south, speeding erosion on the 75-mile-long seashore, according to coastal geologist Orrin Pilkey, a professor at Duke University.

Constricting the inlet also could create pressure during storms that would send waves crashing through another part of the coast, possibly in Nags Head, Pilkey said.

The corps proposes to duplicate the sand movements with a massive pumping machine, moving sand around the jetties and depositing it on shores to the south. But Gogue said this would mean moving enough sand each year to fill a tank three miles long, six feet tall and six feet wide.

Several studies put the cost of maintaining the jetties over several decades at $500 million or more.

The corps initially reported that benefits, such as economic development and safety, would exceed costs by 14 cents on every dollar. But corps officials recently acknowledged a "fundamental error" in this equation and are recalculating. The House voted recently to put $1 million in the 1984 budget for the jetties.

Dredging the channel is the cheapest alternative and ecologically the safest, Interior Department officials argue. Pilkey agrees. The corps is now dredging, but its engineers and many fishermen in Wanchese contend that this, too, will hasten erosion and will not do the job.

"Our extensive studies show that jetties are the only way that inlet is ever going to be kept open," said Bob Dawson, deputy assistant secretary of the Army for civil works. Nonetheless, he, too, expresses awe over the forces at work around Hatteras.

"Nature is apparently going to have its way no matter what man does," he said. "The question is how you give those folks as much navigation time as they can get."

Meanwhile, Watt appears to have disappointed his fans in Wanchese. As Etheridge sees it from his struggling packing house:

"I like the man myself. He took on all the environmentalists and that type of people for the oil companies. I guess he just doesn't consider the fishing industry in North Carolina important enough to take the flak."