President Reagan stood on the bunting-draped deck of a refitted World War II battleship today and declared his unswerving commitment to his defense budget and U.S. "maritime superiority" over the Soviets.

In a bristling defense of his military buildup, just a few days before he must begin making budget decisions, Reagan said critics who believe that the Defense Department is "inherently wasteful and unconcerned about cost cutting" are "dead wrong."

He also assailed defense policies that he said were pursued during the 1970s, when military spending in constant dollars decreased by 22 percent and the size of the U.S. Navy dwindled from more than 1,000 ships to 453.

"Potential adversaries saw this unilateral disarmament, which was matched in all the other services, as a sign of weakness and a lack of the will necessary to protect our way of life," Reagan said.

Two Republican presidents, Richard M. Nixon and Gerald R. Ford, were in the White House for six of the 10 years during which Reagan said this "unilateral disarmament" occurred.

Reagan again dismissed the Soviet "zero-option" proposal for arms reductions, in which Soviet President Yuri V. Andropov offered to dismantle some medium-range missiles in Europe in exchange for a U.S. pledge to forgo deployment of similar weapons next year.

"I may say the news is encouraging--the Soviet Union has met us half way on our zero-option," Reagan said. "They have proposed zero on our part."

The president's showcase for his argument that the Pentagon is using its resources efficiently was the USS New Jersey, the 58,000-ton, high-technology battleship he recommissioned today.

The New Jersey, awarded 15 battle stars for its service during World War II and the Korean and Vietnam wars, was converted at a cost of $326 million into a warship equipped with the latest in missiles, electronic warfare and communications technology. With its missiles and 16-inch naval guns it is expected to augment the firepower of the Navy's air arm.

"She is more than the best means of quickly adding real firepower to our navy," Reagan said to a crowd of 9,000, many of them members of the military, shipyard workers and their families. "She is a shining example of how this administration will rebuild America's armed forces: on budget, on schedule and with the maximum cost-effective application of high technology to existing assets."

Secretary of the Navy John F. Lehman Jr., who introduced the president at the ceremony at the Long Beach Naval Shipyard, called the New Jersey "the most modern warship in the world."

It can travel at more than 35 knots, and its 16-inch guns can put one-ton shells on targets more than 20 miles away. Its armaments include 32 Tomahawk missiles, used for sea or land attack, 16 sea-skipping Harpoon anti-ship missiles and four Vulcan Phalanx weapon systems used for close-in defense against aircraft and missiles.

Lehman maintains that the French-built Exocet missile, which sank the British cruiser Sheffield and damaged two other British ships during the Falklands fighting, would bounce off the New Jersey, whose armor alone weighs more than any U.S. cruiser.

But Lehman's view is not held unanimously by naval experts or Republican members of Congress.

Some maintain that battleships, even those as modern as the New Jersey, are too slow and too vulnerable to function effectively in a world of nuclear weapons. Sen. Barry Goldwater (R-Ariz.) has called the New Jersey "a sitting duck."

Opposition to the New Jersey also was expressed today by a handful of demonstrators who were kept outside the shipyard gates with their signs that called for greater spending on domestic programs and less for military purposes.

"Let them eat battleships," read one poster.

However, Reagan remains strongly committed to the view that old battleships should be refitted, both for military and budgetary reasons.

"We have been questioned for bringing back this batteship, yet I would challenge anyone who has been aboard or even seen the New Jersey to argue its value," the president said. "It seems odd and a little ironic to me that some of the same critics who accuse us of chasing technology and gold-plating on weapons systems have led the charge against a superbly cost-effective and maintainable New Jersey."

The president's speech today reflected his increased concern about congressional critics of both parties who have called for closer scrutiny of military spending.

"To those who have been led to believe that we have gone overboard on national security needs and are spending a disproportionate share on the miltitary, let me state that this is not true," Reagan said. "In spite of all the sound and fury that we hear and read, defense spending as a percentage of GNP [gross national product] is well below what it was in the Eisenhower and Kennedy years."

The president quoted Theodore Roosevelt today, calling the Navy "the right arm of the United States and emphatically the peacemaker."

And he finished his litany to the virtues of American military strength by quoting Robert Peniston, captain of the New Jersey when it was decommissioned in 1969. Peniston said then that the battleship should "rest well, yet sleep lightly; and hear the call, if again sounded, to provide firepower for freedom." CAPTION: Picture, Reagan reviews Marines at the recommissioning of the USS New Jersey, a World War II battleship equipped with missiles and other technology at a cost of $326 million. AP