Sybert's letter stresses, as do other proponents of SDI, its defensive nature in that it will deter a first strike.
Perhaps the Soviets don't see SDI as defensive, rather as actually encouraging a first strike. Their logic might go as follows:
"Reagan says he will offer SDI technology, once perfected, to the whole world including us. We don't believe this for a moment. Just as he wouldn't believe us if we were to make a similar offer. And even if he's sincere, what guarantee is there that Presidents to follow would pursue the same course? Thus, in the worst case one must assume that the United States will have a more effective SDI than we. Given this, what's to prevent the Americans from launching a preemptive first strike, knowing that a limited retaliatory strike will be contained by SDI?"
So how do SDI strategists answer this one?