How we change what others think, feel, believe and do
Make promises that you know that you will not have to keep.
Or make what sounds like a promise by adding a qualifier (e.g. 'could') or by making the statement vague.
Use this to get things moving when the negotiation is stuck and the item being requested seems relatively minor.
I don't see why I can't come back some time.
I guess I could spend extra time with you.
Why not? I'm sure I can find the time.
When the other person is fixated on getting something, particularly if it is minor, then they may well be more trapped by the wanting rather than really want it. Suggesting that you will give it to them gives them closure for now and lets you move on with the rest of the negotiation.
This works better for things that will be delivered at an uncertain time in the future. When asked, you can then delay delivery. If pressed, you may actually have to deliver.
As any deceptive method, this holds the danger that it will cause betrayal response.