Initial cost of sila work for MXs put at $7 billion

It would cost up to $7 billion to harden existing silos for deployment of the new MX nuclear missiles, the Air Force says. That would only be a temporary measure until deciding a permanent method of basing the missiles.

President Reagan's modernization plan also includes 100 interim B-1 bombers, at an estimated cost of $20 billion. That part of the proposal ran into trouble in a Senate panel Wednesday when one senator said he'd been told by CIA officials that the current B-52 bombers would be able to penetrate Soviet airspace until 1990.

The Pentagon claims the B-52 will be obsolete by the mid-1980s and is urging that the B-52 fleet be replaced with the 100 B-1s.