What Dobrynin did NOT know was how the United States would replace the obsolete Jupiter missiles. Nuclear Polaris submarines, with Polaris missiles aboard, would more than adequately protect Turkey from a Soviet attack. The proposal Bobby Kennedy made was not a trade after all.
The Attorney General described his version of the Turkey missile discussion in a top secret memo for Dean Rusk. (this is a PDF link)
He then asked me about Khrushchev's other proposal dealing with the removal of the missiles from Turkey. I replied that there could be no quid pro quo - no deal of this kind could be made...I said it was completely impossible for NATO to take such a step under the present threatening position of the Soviet Union. If some time elapsed - and per your instructions, I mentioned four or five months - I said I was sure that these matters could be resolved satisfactorily.
Bobby stressed he was not proposing a deal:
Per your instructions I repeated that there could be no deal of any kind and that any steps toward easing tensions in other parts of the world largely depended on the Soviet Union and Mr. Khrushchev taking action in Cuba and taking it immediately.
Urging Dobrynin to get a prompt response from the Kremlin, Kennedy concludes his memo:
I repeated to him that this matter could not wait and that he had better contact Mr. Khrushchev and have a commitment from him by the next day to withdraw the missile bases under United Nations supervision for otherwise, I said, there would be drastic consequences.
The next morning Khrushchev responded.