The administration has given Congress pictures and additional information about the Soviet Union's new mobile 10-warhead SS24 intercontinental missile as part of its effort to gain votes for additional funding for the 10-warhead MX that President Reagan wants to build.
Sen. James A. McClure (R-Idaho) used newly released data and a Pentagon illustration of the SS24 during a speech on the Senate floor in support of the MX missile earlier this week.
The drawing was done from intelligence photographs of the missile, which will not be operational until next year.
McClure said that railroad cars attached to the missile launcher will house additional missiles, support equipment, security forces and command and control facilities.
"These trains are deceptively concealed," McClure said, "so as to appear externally identical to standard Soviet freight trains."
The Soviets also have developed and are deploying a second new mobile missile, the SS25, which has a single warhead and is transported on trucks.
Some arms control experts say that the SS25 is more "potentially unsettling" than the SS24.
John D. Steinbruner, director of the Brookings Institution's national security program and a former Pentagon consultant, said the Soviets so far have "made it easy for us" to keep track of SS25s by constructing unique garages for them.
But, he said, the deployment of the SS25 is disturbing because the Reagan administration "does not appear to be making any efforts to control it by arms control arrangements."
"If they decide to go to concealment," he added, "it would begin a very unfavorable competition because we don't have the land and the population control they have to permit those activities."
The SS25 "is nearing operational capability" in two missile fields, according to the new version of "Soviet Military Power," the Pentagon's annual survey of Moscow's military forces. The volume is scheduled to be released next month.
Steinbruner said yesterday that administration officials have yet to reach agreement on what negotiating position to take on the two new Soviet mobile missiles at the Geneva talks.
The Soviets have informed the United States that the SS24 is the one new missile permitted under terms of the unratified SALT II treaty.
They have also said the SS25 is a permitted modification of their older SS13 missile.
Up to now, the administration has described the SS25 as a violation of SALT II provisions because it is significantly different from the SS13.
A Pentagon official said yesterday that beyond protesting the SS25, "there is no consensus within the government about what the Soviets should do with it."
Steinbruner and other intelligence experts said yesterday that it would be easier to keep track of the larger SS24 on its railroad launcher once it became operational than it would to follow the smaller road-mobile SS25.
Last Sunday, Secretary of State George P. Shultz said, "The mobility of missiles increasingly raises problems about verification, whether you can really count them and know how many there are and where they are."
Steinbruner echoed that view but added that the administration did "not want to acknowledge this major Soviet weapons initiative that could be troublesome in the future."