The policy laid out by President Carter in his defense speech yesterday would push defense spending over $200 billion within five years, bid farewell to the Nixon Doctrine, and commit the nation to building a wide array of new weapons.

his blueprint for the nation's future defenses amounts to scrapping the one he sketched out as a presidential candidate in 1976 when he recommended cutting military spending by from $5 billion to $7 billion.

The Pentagon in this current fiscal year -- 1980 -- is expected to end up with $138.6 billion in budget authority and actually spend $127.4 billion. Carter's plan for fiscal 1981 calls for raising those catagories to $157 billion and $142 billion, with inflation assumed to be 8.3 percent.

To make good on his promise yesterday to increase those amounts "more than 4 1/2 percent as year" after allowing for inflation, the defense budget would top $200 billion as early as fiscal 1983.

To accommodate an inflation rate of 9 percent or so and still achieve the 4 1/2 percent real increase, the Pentagon budgets from 1981 onward would have to go up by about 14 percent. This would mean $204 billion in budget authority by fiscal 1983, and $208 billion in actual spending by fiscal 1984.

A White House official acknowledged yesterday that this sharp climb in defense spending would mark a turnaround by the president. The official explained the switch by declaring that Carter's hopes for negotiating deep cutbacks in U.S. and Soviet arms had not been realized.

The president's speech committed the administration to building quick reaction forces that could intervene in trouble spots all around the world, in contrast to the Nixon Doctrine, which called for foreign governments to provide the manpower.

An administration official, who under the ground rules of the White House briefing could not be identified, underscored the section of the president's speech that said "we must understand that not every instance of the firm application of power is a potential Vietnam."

The so-called Rapid Deployment Force is designed to provide the president with the option of rushing American troops to remote corners of the world, not just sending in weaponry or other military aid, which was the heart of the Nixon Doctrine.

Carter's fiscal 1981 budget requests money to start building a fleet of cx cargo planes that could carry tanks, Marines and Army troops of this force to the Persian Gulf and other likely trouble spots. The new budget also earmarks money to build cargo ships for military gear to be pre-positioned in the Mideast and other areas where conflicts might occur.

Carter, as another part of his plan to make it easier to project American military power around the world, promised to build a Navy of 550 ships by "the 1990s." That will take some doing.

The Navy is expected to have 462 ships in the fleet by the end of this fiscal year. But many of them will wear out in the late 1980s and early 1990s, and it will cost billions of dollars to replace them.

Carter signaled yesterday that he will not settle for smaller and cheaper ships, declaring: "We will continue to build the most capable ships afloat" because "seapower is indensable to our global strategy."

Modern warships like the Nimitz nuclear aircraft carrier cost more than $2 billion each. Navy leaders insist they need expensive ships as the Aegis destroyers to combat the Soviet threat. Carter's promise sounds like a victory for them.

The president also reaffirmed his commitment to the MX blockbuster nuclear missile that the Air Force intends to deploy in Utah and Nevada. He referred obliquely to the weapon's first strike, or "counterforce," nature by saying the MX "will have the capability to attack a wide variety of Soviet military targets."

The White House official who briefed reporters on the speech said that the president may go beyond the cruise missiles already being flight-tested and build longer-range ones. This would enable the aircraft carrying the missiles to fire them at a safer distance from the target.

Besides building up the Navy and deploying nuclear-tipped strategic weapons, like the MX and cruise missile, Carter promised to modernize the forces designed to fight a nonnuclear war.

Although the armed forces are finding it difficult to fill their ranks with volunteers, Carter served notice that he was sticking with the All-Volunteer Force rather than return to the draft suspended in 1973.

"I am determined to recruit and to retain an ample level" of "skilled and experienced military personal," the president said.

Sen. Sam Nunn (D. Ga.), who was at the forefront of those demanding higher defense spending to make the pending strategic arms limitation treaty an acceptable risk to them, said through a spokesman last night that he would not comment on Carter's new budget plan until after today's Senate Armed Services Committee hearing on it.

Carter in June 1976 wrote the Democratic platform commitee that "without endangering the defense of our nation or our commitments to our allies, we can reduce present defense expenditures by about $5 billion to $7 billion annually."

His speech yesterday shows that he has chosen a far different path.