Refuse to Remove Missiles
You send word to Kennedy that the missiles will be staying right where they were. They are there for protection. They are there to deter the United States from doing anything to harm Cuba.
From what you know of Kennedy, he is all bark and no bite. He talks a good game, but underneath that exterior, he's just a small man who is afraid to risk conflict.
He'll just whine, and whine, and whine some more...