The Air Force now estimates that by 1989 the Soviet Union could have so many accurate nuclear warheads that as little as 1 percent of the U.S. land-based missile force might survive "a well-executed Soviet first strike."

That estimate, contained in a chart just sent to Congress, is lower than any previous Pentagon projection.

Congressional critics of the proposed MX missile are seizing on the chart because it suggests that by the end of this decade only one of the 100 MXs President Reagan wants to deploy could survive an attack.

An Air Force official confirmed that the "worst case" estimate in the chart goes below the 5 percent survival rate for land missiles given to Congress in the past.

The official noted, however, that Reagan's new plan for the land-based part of the nation's nuclear offensive force calls also for moving in the future to a mobile and harder-to-hit smaller missile nicknamed "Midgetman." He said other ways to protect land missiles will be explored as well while the MXs are being placed in existing and admittedly vulnerable Minuteman silos.

Also, he said, the low survival rates assume that Soviet growth in warheads will be "unconstrained" by arms-control agreements sought by the president.

Despite these caveats, MX opponents in Congress yesterday were preparing speeches citing the new estimate.

One such critic, Sen. Carl Levin (D-Mich.), said in a recent heated exchange with Pentagon research director Richard D. DeLauer that it makes little sense to spend $20 billion for 100 missiles when only five--he was using the old 5 percent figure--could survive the kind of strike the Soviets could launch late in this decade.

The chart at issue is a crudely drawn one that shows that from 10 to 35 percent of the U.S. land missile force would survive an attack by today's Soviet forces. The survival estimates drop to between 1 and 7 percent for 1989.

"Soviets probably possess the capability to destroy almost all of the 1,047 U.S. ICBM silos, using only a portion of their own ICBM forces," said the Air Force in its "point paper" containing the chart. "Shown below is the expected percentage of survivors following a well-executed Soviet first strike on existing U.S. silos."

The Air Force said that the chart does not address such Soviet uncertainties as whether the United States would fire its land missiles during an attack and whether the Soviets could "confidently attack all legs of triad," the Pentagon term for the U.S. nuclear arsenal containing land missiles, sea missiles and bombers, some of them armed with cruise missiles.

Each MX would carry 10 warheads. Under the 1989 Air Force projections, from 10 to 70 warheads could survive a Soviet attack if the Soviets keep deploying accurate warheads.

The survival estimates came as the administration continued to push for votes on the MX in both houses of Congress next week; it wants held-up engineering and testing money released before the legislators go home for the Memorial Day recess. Congress refused to release the funds last winter because it was dissatisfied with the administration's plan for deploying the MX. Reagan has since submitted a new deployment proposal.

Opponents of the new ICBM wanted to delay the vote until after the recess, so that, as one said, the members "could learn when they go home that this deal only sells within the Beltway."

One Democrat working with the White House said yesterday that the pro-MX vote stood at 223, five more than needed for passage. He said that the pro-MX contingent was made up of 150 Republicans and 73 Democrats, with another 58 Democrats counted as still undecided.

Anti-MX lobbyists claimed about 200 votes on their side, but as one put it yesterday, "that was before the House Appropriations Committee vote Tuesday." That vote was 30 to 26. Last year, when the appropriations panel had a tie vote Gloomy Air Force Estimate Missile Survival Questioned By George C. Wilson and Walter Pincus Washington Post Staff Writers

The Air Force now estimates that by 1989 the Soviet Union could have so many accurate nuclear warheads that as little as 1 percent of the U.S. land-based missile force might survive "a well-executed Soviet first strike."

That estimate, contained in a chart just sent to Congress, is lower than any previous Pentagon projection.

Congressional critics of the proposed MX missile are seizing on the chart because it suggests that by the end of this decade only one of the 100 MXs President Reagan wants to deploy could survive an attack.

An Air Force official confirmed that the "worst case" estimate in the chart goes below the 5 percent survival rate for land missiles given to Congress in the past.

The official noted, however, that Reagan's new plan for the land-based part of the nation's nuclear offensive force calls also for moving in the future to a mobile and harder-to-hit smaller missile nicknamed "Midgetman." He said other ways to protect land missiles will be explored as well while the MXs are being placed in existing and admittedly vulnerable Minuteman silos.

Also, he said, the low survival rates assume that Soviet growth in warheads will be "unconstrained" by arms-control agreements sought by the president.

Despite these caveats, MX opponents in Congress yesterday were preparing speeches citing the new estimate.

One such critic, Sen. Carl Levin (D-Mich.), said in a recent heated exchange with Pentagon research director Richard D. DeLauer that it makes little sense to spend $20 billion for 100 missiles when only five--he was using the old 5 percent figure--could survive the kind of strike the Soviets could launch late in this decade.

The chart at issue is a crudely drawn one that shows that from 10 to 35 percent of the U.S. land missile force would survive an attack by today's Soviet forces. The survival estimates drop to between 1 and 7 percent for 1989.

"Soviets probably possess the capability to destroy almost all of the 1,047 U.S. ICBM silos, using only a portion of their own ICBM forces," said the Air Force in its "point paper" containing the chart. "Shown below is the expected percentage of survivors following a well-executed Soviet first strike on existing U.S. silos."

The Air Force said that the chart does not address such Soviet uncertainties as whether the United States would fire its land missiles during an attack and whether the Soviets could "confidently attack all legs of triad," the Pentagon term for the U.S. nuclear arsenal containing land missiles, sea missiles and bombers, some of them armed with cruise missiles.

Each MX would carry 10 warheads. Under the 1989 Air Force projections, from 10 to 70 warheads could survive a Soviet attack if the Soviets keep deploying accurate warheads.

The survival estimates came as the administration continued to push for votes on the MX in both houses of Congress next week; it wants held-up engineering and testing money released before the legislators go home for the Memorial Day recess. Congress refused to release the funds last winter because it was dissatisfied with the administration's plan for deploying the MX. Reagan has since submitted a new deployment proposal.

Opponents of the new ICBM wanted to delay the vote until after the recess, so that, as one said, the members "could learn when they go home that this deal only sells within the Beltway."

One Democrat working with the White House said yesterday that the pro-MX vote stood at 223, five more than needed for passage. He said that the pro-MX contingent was made up of 150 Republicans and 73 Democrats, with another 58 Democrats counted as still undecided.

Anti-MX lobbyists claimed about 200 votes on their side, but as one put it yesterday, "that was before the House Appropriations Committee vote Tuesday." That vote was 30 to 26. Last year, when the appropriations panel had a tie vote on the MX, production funds for the missile were beaten overwhelmingly on the House floor.

"We should have a decent chance on the floor, but the White House is all over the place today," one Capitol Hill opponent said yesterday. on the MX, production funds for the missile were beaten overwhelmingly on the House floor.

"We should have a decent chance on the floor, but the White House is all over the place today," one Capitol Hill opponent said yesterday