How Does the Risk-Free Rate Affect the Delta of Deep ITM Put Options?

A high-interest rate environment slightly decreases the Delta of deep ITM put options (makes it closer to -1.0). Higher rates decrease the present value of the strike price, making the put option less valuable relative to the underlying asset.

This effect marginally pushes the put Delta further away from 0 and closer to -1.0, though the change is very small for deep ITM options.