The Carter administration intends to ask Congress for $1 billion for new civil defense preparations, a symbolic decision on the side of officials who have argued that the United States must match Soviet capabilities to wage nuclear war.

The decision - taken by President Carter over the advice of officials in the State Department and the Arms Control and Disarmament Agency - is to ask Congress to finance drafting of a new doomsday plan for evacuating city-dwellers to the country to escape the effects of nuclear attack.

According to official sources, the administration has opted for this new plan in part to woo critics of a new strategic arms control treaty (SALT) with the Soviet Union, in part to embrace the view that the United States must be able to match Soviet options in a nuclear crisis. The Soviets have a substantial civil defense program, according to U.S. intelligence estimates.

Both National Security Affairs adviser Zbigniew Brzezinski and Defense Secretary Harold Brown backed this idea, sources said. Col. William Odom, an assistant to Brzezinski did much of the staff work on the new civil defense plan.

Carter, in signing Presidential Directive 41 on Sept. 29, launched the "crisis relocation program," which is expected to get about $140 million in his fiscal 1980 budget, now in preparation, compared to the $96.5 million a year now spent on civil defense.

Critics of spending more for civil defense, including some ACDA officials, contend that this would be a waste of money in this day of H-bombs, which can kill by blast or fallout. They contend the Soviet civil defense effort is of little value and should not be duplicated by the United States.

Critics of evacuation further warn that the sight of people leaving cities would only heat up an international crisis but also make it more likely that missiles would be fired.

Civil defense planning became a subject of public concern during the 1950s when President Eisenhower justified the multibillion-dollar interstate highway system on civil defense grounds. In the early 1960s, with rising concern over the possibility of nuclear war, President Kennedy launched a civil defense program that stressed bomb shelters, food stock-piles and dispersal techniques for urban school populations.

At a Pentagon news conference yesterday, Bardyl R. Tirana, director of the Defense Civil Preparedness Agency, formulated the administration's case for going ahead with an evacuation plan.

Tirana said Carter had made a "policy decision that civil defense can play a small and modest role in our strategic deterrence."

He stressed that Carter is not calling for digging blast shelters for the general population, a government civil defense initiative that blew up on the launching paid in the 1960s, but is limiting the effort to dispersel.

The idea, Tirana continued, is to evacuate people from the "high-risk areas," such as missile bases and cities, to "host areas" in the countryside. How they would live once they reached the countryside is one of the issues planners must address, he said.

If people were evacuated before nuclear warheads hit cities and military targets, Tirana estimated the number of survivors from a population of 220 million would increase by as many as 70 million. Without an evacuation plan, he estimated that between 80 million and 90 million might survive. With evacuation, he estimated the number could increase to between 140 million and 150 million.

He conceded that evacuating people quickly from the congested northeast corridor or from California during a crisis would be "among the most difficult" problems to solve.

He said the idea is to have no more than three evacuees for every person in the "host area" in the countryside, but added that the ratio would be more than double that in area outside California.

Asked if people would be receptive to another civil defense program, Tirana replied: "The mood of the public varies from town to town."

He said what the administration is doing is "facing up to the fact that we have very little ability of protecting our population from the consequences of nuclear attack."

"My sense is that I would not want to see a situation where the Soviet Union had the potential to protect its population and we had done nothing to protect our own," he said, adding that such a situation would be "destabilizing."

He conceded that an evacuation plan "does not solve the problem of fallout" and "does not solve the enormous human problems" that would come from a nuclear war between the United States and the Soviet Union.

He said that the very existence of an American evacuation plan on paper might deter the Soviets from implementing their plans for sending people out of cities and other high-risk areas during a crisis.

Asked if civilians evacuating cities might not increase the likelihood that missiles would be fired, Tirana said it was vital that the United States consider a dispersal plan as an option to be exercised only in response to Soviet evacuation.

"I would never contemplate" evacuating Americans during a crisis "unless we knew people were walking out of Moscow and Leningrad," he said.

Asked if evacuation plans might impel U.S. and Soviet war planners to go back to deploying nuclear weapons that would be more effective in killing civilians with fallout, especially if the weapons were exploded on the ground rather than above a missile field, Tirana said this was out of his area of expertise.

The civil defense director said that "Congress will unquestionably ask what are th long-range implications" of drafting a long-range plane for evacuating civilians.

Although he would not give a specific figure for the plan, Tirana has said in the past that it could run $1.15 billion over five years.

Whatever problems the United States would encounter in evacuating civilians in a crisis, the "Soviet Union would have the same or greater logistical problems," he said. The U.S. evacuation plan "could be as effective" as the Soviet one "or more so," he said.

Staff writer Robert G. Kaiser contributed to this article.