Two-time world champion Alonso is among those drivers whose future beyond this year is uncertain and the Spaniard has been linked with the vacant Mercedes seat to partner George Russell.
The 42-year-old is currently weighing up his options, as he is keen to stay at Aston Martin if the project is there, but he has also stressed that retirement is an option he is considering.
Krack: Aston must give Alonso a quick car
Speaking with f1i.com, team boss Krack admitted that Aston Martin must give Alonso a ‘quick car’ to retain him for the future.
"It is clear that a driver of that calibre is attractive for everybody, that is clear but we will try to keep him,” he said.
"It is no secret that he first of all wants to decide for himself what he wants to do.
"We want to continue working with Fernando, and I think the most important thing is that we give him a quick car so he believes in this project, believes in this team - and everything else we will have to discuss over the weeks to come.”
Krack also highlighted his leadership qualities and experience along with his driving ability as to why they are determined to keep him on board.