Motherwell manager Stuart McCall has targeted Samson as a replacement for Darren Randolph, who will leave Fir Park at the end of the season, with Birmingham his expected destination.
Speaking after his side's goalless draw with Aberdeen, Danny Lennon said: "We got correspondence from Motherwell yesterday and they are going to open up negotiations.
"He has been absolutely fantastic for us and we felt, for a club our size working within our budgets, that we made a good offer.
"Sammy has declined that and taken a bit of a gamble. He believes in his ability and let's see where it takes us.
"But he has been absolutely terrific, a top bloke. To see him coming in as number two to Paul Gallacher, then picking up the reins and getting into the Scotland set-up, and he could now be at the runners-up of the SPL. We will see where that one goes."
Lennon has already had a potential replacement in training in the form of Kyle Letheren, who left Kilmarnock last month.
"We had a look at him and he handled himself very well," Lennon said.