Gen. Alexander Haig said yesterday that deploying the neutron warhead in Europe would decrease rather than increase the chance that nuclear war would be waged there.

The North Atlantic Treaty Organization commander told a Pentagon news conference that the new weapon would have more credibility in the eyes of the Soviets than the tactical nuclear weapons now in Europe.

If the Soviets are forced to assume that this new neutron warhead is more likely to be used than today's nuclear weapons, said Haig, they are less likely to launch an attack on NATO in the first place.

"The utility of the weapon; its usability; its credibility generally in deterrence terms," said Haig of the neutron warhead, "contributes to the reality that it will not have to be used . . . It's our military view" that the neutron warhead "raises, not lowers, the nuclear threshold."

While stressing tht whether the neutron warhead is deployed in Europe is a political question, Haig said that from a "purely military point of view we feel it is a most desirable modernization step to be undertaken by the alliance."

The neurton warhead, upon exploding, penetrates armor with lethal neutrons, increasing the probability of killings crews inside tanks without destroying the hardware. Haig yesterday called the weapon "a system more discriminating" and one "which achieves greater military effect with less collateral damage."

Deploying the neutron warhead, Haig said, would "not modify, change or alleviate the procedures or the anguishing decision that must be made by appropriate political authorities for any resort to nuclear weapons."

The commander said "military authorities in NATO" believe it "is somewhat Iudicrous" to focus "so much attention" on the U.S. neutron warhead "and so little" on the Soviet SS-20 missile targeted on NATO which "is 2,000 times more devastating in its explosive consequence."

He said the Soviets "are rapidly approaching parity" with NATO in tactical nuclear weapons and have developed nuclear rounds for their conventional artillery. These nuclear artillery shells have not been deployed near the NATO front line, Haig said, but would put "our parity in serious jeopardy" if they were deployed there.